From 75437da58196ec9d67b1d002b671229dbb74b99c Mon Sep 17 00:00:00 2001
From: Alec Geatches <alec.geatches@automattic.com>
Date: Mon, 22 Apr 2024 13:15:19 -0600
Subject: [PATCH 1/9] Increase composer.json required PHP version to 7.4

---
 composer.json | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/composer.json b/composer.json
index 935b0b97..e55cb0c8 100644
--- a/composer.json
+++ b/composer.json
@@ -23,7 +23,7 @@
 	},
 	"require": {
 		"composer/installers": "~1.0",
-		"php": ">=5.6"
+		"php": ">=7.4"
 	},
 	"require-dev": {
 		"automattic/vipwpcs": "^2.2",

From fdce51cafaa26fa232bf9796341381cda41eaff4 Mon Sep 17 00:00:00 2001
From: Alec Geatches <alec.geatches@automattic.com>
Date: Mon, 22 Apr 2024 13:19:08 -0600
Subject: [PATCH 2/9] Update README to match required PHP version 7.4

---
 README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/README.md b/README.md
index dccda58c..94ce3833 100644
--- a/README.md
+++ b/README.md
@@ -3,7 +3,7 @@
 Stable tag: 3.6.0  
 Requires at least: 4.1  
 Tested up to: 6.5  
-Requires PHP: 5.6  
+Requires PHP: 7.4  
 License: GPLv2 or later  
 License URI: https://www.gnu.org/licenses/gpl-2.0.html  
 Tags: authors, users, multiple authors, co-authors, multi-author, publishing  

From da21813fc0e8e01714e72da1477523cd97fb91d8 Mon Sep 17 00:00:00 2001
From: Alec Geatches <alec.geatches@automattic.com>
Date: Mon, 22 Apr 2024 13:24:38 -0600
Subject: [PATCH 3/9] Remove PHP 7.1 from integration tests

---
 .github/workflows/integrate.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/integrate.yml b/.github/workflows/integrate.yml
index ed42ed30..ff3caa44 100644
--- a/.github/workflows/integrate.yml
+++ b/.github/workflows/integrate.yml
@@ -14,7 +14,7 @@ jobs:
     strategy:
       matrix:
         wordpress: [ '5.7', '6.3' ]
-        php: [ '7.1', '7.4', '8.0', '8.2' ]
+        php: [ '7.4', '8.0', '8.2' ]
         allowed_failure: [ false ]
         include:
           # Check upcoming WP.

From fd9b266c619666a203bf9e403ef5e9158727c16e Mon Sep 17 00:00:00 2001
From: Gary Jones <gary.jones@automattic.com>
Date: Tue, 23 Apr 2024 16:19:51 +0100
Subject: [PATCH 4/9] PHP 7.4: Use array_key_first()

Slightly cleaner to use the native function for getting the first key's value from an array.
---
 .../block-coauthor-avatar/class-block-coauthor-avatar.php   | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/php/blocks/block-coauthor-avatar/class-block-coauthor-avatar.php b/php/blocks/block-coauthor-avatar/class-block-coauthor-avatar.php
index b9541cfa..52e47f6f 100644
--- a/php/blocks/block-coauthor-avatar/class-block-coauthor-avatar.php
+++ b/php/blocks/block-coauthor-avatar/class-block-coauthor-avatar.php
@@ -6,7 +6,7 @@
  * @since 3.6.0
  */
 
-namespace CoAuthors\Blocks; 
+namespace CoAuthors\Blocks;
 
 use WP_Block;
 /**
@@ -52,12 +52,12 @@ public static function render_block( array $attributes, string $content, WP_Bloc
 		if ( empty( $avatar_urls ) ) {
 			return '';
 		}
-		
+
 		$display_name = esc_html( $author['display_name'] ?? '' );
 		$link         = esc_url( $author['link'] ?? '' );
 		$is_link      = '' !== $link && $attributes['isLink'] ?? false;
 		$rel          = $attributes['rel'] ?? '';
-		$size         = $attributes['size'] ?? array_keys( $avatar_urls )[0];
+		$size         = $attributes['size'] ?? array_key_first( $avatar_urls );
 		$align        = esc_attr( $attributes['align'] ?? '' );
 
 		$srcset = array_map(

From 2c4c9ecc380c20fd3940d436c3959783ba0ebfd3 Mon Sep 17 00:00:00 2001
From: Gary Jones <gary.jones@automattic.com>
Date: Tue, 23 Apr 2024 16:26:45 +0100
Subject: [PATCH 5/9] PHP 7.4: Use instanceof

---
 php/api/endpoints/class-coauthors-controller.php |  6 +++---
 php/blocks/class-blocks.php                      | 14 +++++++-------
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/php/api/endpoints/class-coauthors-controller.php b/php/api/endpoints/class-coauthors-controller.php
index 7faef532..3166ec89 100644
--- a/php/api/endpoints/class-coauthors-controller.php
+++ b/php/api/endpoints/class-coauthors-controller.php
@@ -164,7 +164,7 @@ public function get_item( $request ) {
 	 * @param WP_User|stdClass $coauthor
 	 */
 	public static function is_coauthor( $coauthor ): bool {
-		return is_a( $coauthor, 'WP_User' ) || self::is_guest_author( $coauthor );
+		return $coauthor instanceof \WP_User || self::is_guest_author( $coauthor );
 	}
 
 	/**
@@ -320,10 +320,10 @@ public function get_item_schema(): array {
 	 * @return WP_REST_Response|WP_Error
 	 */
 	public function prepare_item_for_response( $author, $request ) {
-	
+
 		$fields = $this->get_fields_for_response( $request );
 
-		if ( is_a( $author, 'WP_User' ) ) {
+		if ( $author instanceof \WP_User ) {
 			$author              = $author->data;
 			$author->description = get_user_meta( $author->ID, 'description', true );
 		}
diff --git a/php/blocks/class-blocks.php b/php/blocks/class-blocks.php
index 2f8abd81..a668d2e9 100644
--- a/php/blocks/class-blocks.php
+++ b/php/blocks/class-blocks.php
@@ -1,7 +1,7 @@
 <?php
 /**
  * Blocks
- * 
+ *
  * @package Automattic\CoAuthorsPlus
  * @since 3.6.0
  */
@@ -13,7 +13,7 @@
 
 /**
  * Blocks
- * 
+ *
  * @package CoAuthors
  */
 class Blocks {
@@ -101,14 +101,14 @@ public static function provide_author_archive_context( array $context, array $pa
 
 	/**
 	 * Block Uses Author Context
-	 * 
+	 *
 	 * @param string $block_name Block name to check for use of author context.
 	 * @return bool Whether the `uses_context` property of the registered block type includes `'co-authors-plus/author'`
 	 */
 	public static function block_uses_author_context( string $block_name ): bool {
 		$block = WP_Block_Type_Registry::get_instance()->get_registered( $block_name );
 
-		if ( ! is_a( $block, 'WP_Block_Type' ) ) {
+		if ( ! $block instanceof \WP_Block_Type ) {
 			return false;
 		}
 
@@ -165,7 +165,7 @@ public static function enqueue_store(): void {
 	 * @return null|array Either an array of data about an author, or null.
 	 */
 	public static function get_author_with_api_schema( $author ): ?array {
-		if ( ! ( is_a( $author, 'stdClass' ) || is_a( $author, 'WP_User' ) ) ) {
+		if ( ! ( $author instanceof \stdClass || $author instanceof \WP_User ) ) {
 			return null;
 		}
 
@@ -199,10 +199,10 @@ public static function get_author_with_api_schema( $author ): ?array {
 
 	/**
 	 * Get CoAuthors with API Schema
-	 * 
+	 *
 	 * Use the global WP_REST_Server to fetch co-authors for a post,
 	 * so that it matches what a user would see in the editor.
-	 * 
+	 *
 	 * @since 3.6.0
 	 * @param int   $post_id Post ID for querying co-authors.
 	 * @param array $data Co-authors as returned by the REST API.

From 5692feb34bf9b02d867d211bdb360e3f3af3d1c0 Mon Sep 17 00:00:00 2001
From: Gary Jones <gary.jones@automattic.com>
Date: Tue, 23 Apr 2024 16:29:53 +0100
Subject: [PATCH 6/9] PHP 7.4: Use null coalescing

---
 php/class-coauthors-endpoint.php      |  2 +-
 php/class-coauthors-guest-authors.php | 28 +++++++++++++--------------
 php/class-coauthors-plus.php          |  4 ++--
 3 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/php/class-coauthors-endpoint.php b/php/class-coauthors-endpoint.php
index 7db6574c..51ef9d07 100644
--- a/php/class-coauthors-endpoint.php
+++ b/php/class-coauthors-endpoint.php
@@ -130,7 +130,7 @@ public function get_coauthors_search_results( $request ) {
 		$response = array();
 
 		$search  = strtolower( $request->get_param( 'q' ) );
-		$ignorable = null === $request->get_param( 'existing_authors' ) ? '' : $request->get_param( 'existing_authors' );
+		$ignorable = $request->get_param( 'existing_authors' ) ?? '';
 		$ignore  = explode( ',', $ignorable );
 		$authors = $this->coauthors->search_authors( $search, $ignore );
 
diff --git a/php/class-coauthors-guest-authors.php b/php/class-coauthors-guest-authors.php
index 5ba9047b..ae14719c 100644
--- a/php/class-coauthors-guest-authors.php
+++ b/php/class-coauthors-guest-authors.php
@@ -109,21 +109,21 @@ public function __construct() {
 		$args = array(
 			'label'               => $this->labels['singular'],
 			'labels'              => array(
-				'name'                  => isset( $this->labels['plural'] ) ? $this->labels['plural'] : '',
-				'singular_name'         => isset( $this->labels['singular'] ) ? $this->labels['singular'] : '',
+				'name'                  => $this->labels['plural'] ?? '',
+				'singular_name'         => $this->labels['singular'] ?? '',
 				'add_new'               => _x( 'Add New', 'guest author', 'co-authors-plus' ),
-				'all_items'             => isset( $this->labels['all_items'] ) ? $this->labels['all_items'] : '',
-				'add_new_item'          => isset( $this->labels['add_new_item'] ) ? $this->labels['add_new_item'] : '',
-				'edit_item'             => isset( $this->labels['edit_item'] ) ? $this->labels['edit_item'] : '',
-				'new_item'              => isset( $this->labels['new_item'] ) ? $this->labels['new_item'] : '',
-				'view_item'             => isset( $this->labels['view_item'] ) ? $this->labels['view_item'] : '',
-				'search_items'          => isset( $this->labels['search_items'] ) ? $this->labels['search_items'] : '',
-				'not_found'             => isset( $this->labels['not_found'] ) ? $this->labels['not_found'] : '',
-				'not_found_in_trash'    => isset( $this->labels['not_found_in_trash'] ) ? $this->labels['not_found_in_trash'] : '',
-				'featured_image'        => isset( $this->labels['featured_image'] ) ? $this->labels['featured_image'] : '',
-				'set_featured_image'    => isset( $this->labels['set_featured_image'] ) ? $this->labels['set_featured_image'] : '',
-				'use_featured_image'    => isset( $this->labels['use_featured_image'] ) ? $this->labels['use_featured_image'] : '',
-				'remove_featured_image' => isset( $this->labels['remove_featured_image'] ) ? $this->labels['remove_featured_image'] : '',
+				'all_items'             => $this->labels['all_items'] ?? '',
+				'add_new_item'          => $this->labels['add_new_item'] ?? '',
+				'edit_item'             => $this->labels['edit_item'] ?? '',
+				'new_item'              => $this->labels['new_item'] ?? '',
+				'view_item'             => $this->labels['view_item'] ?? '',
+				'search_items'          => $this->labels['search_items'] ?? '',
+				'not_found'             => $this->labels['not_found'] ?? '',
+				'not_found_in_trash'    => $this->labels['not_found_in_trash'] ?? '',
+				'featured_image'        => $this->labels['featured_image'] ?? '',
+				'set_featured_image'    => $this->labels['set_featured_image'] ?? '',
+				'use_featured_image'    => $this->labels['use_featured_image'] ?? '',
+				'remove_featured_image' => $this->labels['remove_featured_image'] ?? '',
 			),
 			'public'              => true,
 			'publicly_queryable'  => false,
diff --git a/php/class-coauthors-plus.php b/php/class-coauthors-plus.php
index fb7df6ce..fbee12d1 100644
--- a/php/class-coauthors-plus.php
+++ b/php/class-coauthors-plus.php
@@ -1519,8 +1519,8 @@ public function get_to_be_filtered_caps() {
 	public function filter_user_has_cap( $allcaps, $caps, $args ) {
 
 		$cap     = $args[0];
-		$user_id = isset( $args[1] ) ? $args[1] : 0;
-		$post_id = isset( $args[2] ) ? $args[2] : 0;
+		$user_id = $args[1] ?? 0;
+		$post_id = $args[2] ?? 0;
 
 		if ( ! in_array( $cap, $this->get_to_be_filtered_caps(), true ) ) {
 			return $allcaps;

From c1d7f63f74ba05d404a9fbbc08de1ecfdcb5346c Mon Sep 17 00:00:00 2001
From: Gary Jones <gary.jones@automattic.com>
Date: Tue, 23 Apr 2024 16:47:46 +0100
Subject: [PATCH 7/9] PHP 7.4: Add return types

---
 php/class-coauthors-endpoint.php              | 20 ++---
 php/class-coauthors-guest-authors.php         | 46 +++++-----
 php/class-coauthors-iterator.php              |  8 +-
 php/class-coauthors-plus.php                  | 86 +++++++++----------
 php/class-coauthors-template-filters.php      |  6 +-
 php/class-coauthors-wp-list-table.php         |  6 +-
 php/class-wp-cli.php                          | 38 ++++----
 php/integrations/yoast.php                    | 24 +++---
 php/integrations/yoast/class-coauthor.php     |  6 +-
 tests/Behat/FeatureContext.php                |  6 +-
 tests/Integration/AuthorQueriedObjectTest.php |  4 +-
 tests/Integration/AuthorQueriesTest.php       | 14 +--
 tests/Integration/CoAuthorsPlusTest.php       | 48 +++++------
 tests/Integration/EndpointsTest.php           | 18 ++--
 tests/Integration/GuestAuthorsTest.php        | 48 +++++------
 tests/Integration/ManageCoAuthorsTest.php     | 24 +++---
 .../TemplateTags/CoauthorsGetAvatarTest.php   | 10 +--
 .../CoauthorsPostsLinksSingleTest.php         |  6 +-
 .../TemplateTags/CoauthorsPostsLinksTest.php  |  8 +-
 .../CoauthorsWpListAuthorsTest.php            | 20 ++---
 .../TemplateTags/GetCoauthorsTest.php         | 12 +--
 .../TemplateTags/IsCoauthorForPostTest.php    | 10 +--
 tests/Integration/TemplateTagsTest.php        | 22 ++---
 23 files changed, 246 insertions(+), 244 deletions(-)

diff --git a/php/class-coauthors-endpoint.php b/php/class-coauthors-endpoint.php
index 51ef9d07..96198988 100644
--- a/php/class-coauthors-endpoint.php
+++ b/php/class-coauthors-endpoint.php
@@ -51,7 +51,7 @@ public function __construct( $coauthors_instance ) {
 	/**
 	 * Register endpoints.
 	 */
-	public function add_endpoints() {
+	public function add_endpoints(): void {
 		register_rest_route(
 			static::NS,
 			static::SEARCH_ROUTE,
@@ -126,7 +126,7 @@ public function add_endpoints() {
 	 * @param WP_REST_Request   $request Request object.
 	 * @return WP_REST_Response
 	 */
-	public function get_coauthors_search_results( $request ) {
+	public function get_coauthors_search_results( $request ): WP_REST_Response {
 		$response = array();
 
 		$search  = strtolower( $request->get_param( 'q' ) );
@@ -149,7 +149,7 @@ public function get_coauthors_search_results( $request ) {
 	 * @param WP_REST_Request   $request Request object.
 	 * @return WP_REST_Response
 	 */
-	public function get_coauthors( $request ) {
+	public function get_coauthors( $request ): WP_REST_Response {
 		$response = array();
 
 		$this->_build_authors_response( $response, $request );
@@ -163,7 +163,7 @@ public function get_coauthors( $request ) {
 	 * @param WP_REST_Request   $request Request object.
 	 * @return WP_REST_Response
 	 */
-	public function update_coauthors( $request ) {
+	public function update_coauthors( $request ): WP_REST_Response {
 
 		$response = array();
 
@@ -185,7 +185,7 @@ public function update_coauthors( $request ) {
 	 * @param mixed $param Value to validate.
 	 * @return bool
 	 */
-	public function validate_numeric( $param ) {
+	public function validate_numeric( $param ): bool {
 		return is_numeric( $param );
 	}
 
@@ -194,7 +194,7 @@ public function validate_numeric( $param ) {
 	 *
 	 * @return bool
 	 */
-	public function can_edit_coauthors() {
+	public function can_edit_coauthors(): bool {
 		return $this->coauthors->current_user_can_set_authors();
 	}
 
@@ -205,7 +205,7 @@ public function can_edit_coauthors() {
 	 * @param object  $author The result from co-authors methods.
 	 * @return array
 	 */
-	public function _format_author_data( $author ) {
+	public function _format_author_data( $author ): array {
 
 		return array(
 			'id'           => esc_html( $author->ID ),
@@ -223,7 +223,7 @@ public function _format_author_data( $author ) {
 	 * @param array The response array.
 	 * @param int   The post ID from the request.
 	 */
-	public function _build_authors_response( &$response, $request ) {
+	public function _build_authors_response( &$response, $request ): void {
 		$authors = get_coauthors( $request->get_param( 'post_id' ) );
 
 		if ( ! empty( $authors ) ) {
@@ -237,7 +237,7 @@ public function _build_authors_response( &$response, $request ) {
 	 * Add filters to REST endpoints for each post that
 	 * supports co-authors.
 	 */
-	public function modify_responses() {
+	public function modify_responses(): void {
 
 		$post_types = $this->coauthors->supported_post_types();
 
@@ -266,7 +266,7 @@ public function modify_responses() {
 	 * @param WP_REST_Request   $request  Request object.
 	 * @return WP_REST_Response
 	 */
-	public function remove_author_link( $response, $post, $request ) {
+	public function remove_author_link( $response, $post, $request ): WP_REST_Response {
 		if (
 			! isset( $request['context'] )
 			|| 'edit' !== $request['context']
diff --git a/php/class-coauthors-guest-authors.php b/php/class-coauthors-guest-authors.php
index ae14719c..299f68ea 100644
--- a/php/class-coauthors-guest-authors.php
+++ b/php/class-coauthors-guest-authors.php
@@ -195,7 +195,7 @@ public function filter_post_updated_messages( $messages ) {
 	 *
 	 * @since 3.0
 	 */
-	public function handle_create_guest_author_action() {
+	public function handle_create_guest_author_action(): void {
 
 		if ( ! isset( $_GET['action'], $_GET['nonce'], $_GET['user_id'] ) || 'cap-create-guest-author' !== $_GET['action'] ) {
 			return;
@@ -232,7 +232,7 @@ public function handle_create_guest_author_action() {
 	 *
 	 * @since 3.0
 	 */
-	public function handle_delete_guest_author_action() {
+	public function handle_delete_guest_author_action(): void {
 		global $coauthors_plus;
 
 		if ( ! isset( $_POST['action'], $_POST['reassign'], $_POST['_wpnonce'], $_POST['id'] ) || 'delete-guest-author' != $_POST['action'] ) {
@@ -305,7 +305,7 @@ public function handle_delete_guest_author_action() {
 	 *
 	 * @since 3.0
 	 */
-	public function handle_ajax_search_coauthors_to_assign() {
+	public function handle_ajax_search_coauthors_to_assign(): void {
 		global $coauthors_plus;
 
 		if ( ! current_user_can( $this->list_guest_authors_cap ) ) {
@@ -377,7 +377,7 @@ public function action_parse_request( $query ) {
 	 *
 	 * @since 3.0
 	 */
-	public function action_admin_menu() {
+	public function action_admin_menu(): void {
 
 		add_submenu_page( $this->parent_page, $this->labels['plural'], $this->labels['plural'], $this->list_guest_authors_cap, 'view-guest-authors', array( $this, 'view_guest_authors_list' ) );
 
@@ -388,7 +388,7 @@ public function action_admin_menu() {
 	 *
 	 * @since 3.0
 	 */
-	public function action_admin_enqueue_scripts() {
+	public function action_admin_enqueue_scripts(): void {
 		global $pagenow;
 		// Enqueue our guest author CSS on the related pages
 		if ( $this->parent_page === $pagenow && isset( $_GET['page'] ) && 'view-guest-authors' === $_GET['page'] ) {
@@ -408,7 +408,7 @@ public function action_admin_enqueue_scripts() {
 	 *
 	 * @since 3.0.1
 	 */
-	public function change_title_icon() {
+	public function change_title_icon(): void {
 		?>
 		<script type="text/javascript">
 			jQuery(document).ready(function($){
@@ -423,7 +423,7 @@ public function change_title_icon() {
 	 *
 	 * @since 3.0
 	 */
-	public function action_admin_notices() {
+	public function action_admin_notices(): void {
 		global $pagenow;
 
 		if ( $this->parent_page != $pagenow || ! isset( $_REQUEST['message'] ) ) {
@@ -442,7 +442,7 @@ public function action_admin_notices() {
 	 *
 	 * @since 3.0
 	 */
-	public function action_add_meta_boxes() {
+	public function action_add_meta_boxes(): void {
 		global $coauthors_plus;
 
 		if ( get_post_type() == $this->post_type ) {
@@ -463,7 +463,7 @@ public function action_add_meta_boxes() {
 	 *
 	 * @since 3.0
 	 */
-	public function view_guest_authors_list() {
+	public function view_guest_authors_list(): void {
 
 		// Allow guest authors to be deleted
 		if ( isset( $_GET['action'], $_GET['id'], $_GET['_wpnonce'] ) && 'delete' == $_GET['action'] ) {
@@ -576,7 +576,7 @@ public function view_guest_authors_list() {
 	 *
 	 * @since 3.0
 	 */
-	public function metabox_manage_guest_author_save() {
+	public function metabox_manage_guest_author_save(): void {
 		global $post, $coauthors_plus;
 
 		if ( in_array( $post->post_status, array( 'pending', 'publish', 'draft' ) ) ) {
@@ -596,7 +596,7 @@ public function metabox_manage_guest_author_save() {
 	 *
 	 * @since 3.0
 	 */
-	public function metabox_manage_guest_author_slug() {
+	public function metabox_manage_guest_author_slug(): void {
 		global $post;
 
 		$pm_key        = $this->get_post_meta_key( 'user_login' );
@@ -658,7 +658,7 @@ public function filter_wp_dropdown_users_to_disable( $output ) {
 	 *
 	 * @since 3.0
 	 */
-	public function metabox_manage_guest_author_name() {
+	public function metabox_manage_guest_author_name(): void {
 		global $post;
 
 		$fields = $this->get_guest_author_fields( 'name' );
@@ -691,7 +691,7 @@ public function metabox_manage_guest_author_name() {
 	 *
 	 * @since 3.0
 	 */
-	public function metabox_manage_guest_author_contact_info() {
+	public function metabox_manage_guest_author_contact_info(): void {
 		global $post;
 
 		$fields = $this->get_guest_author_fields( 'contact-info' );
@@ -724,7 +724,7 @@ public function metabox_manage_guest_author_contact_info() {
 	 *
 	 * @since 3.0
 	 */
-	public function metabox_manage_guest_author_bio() {
+	public function metabox_manage_guest_author_bio(): void {
 		global $post;
 
 		$fields = $this->get_guest_author_fields( 'about' );
@@ -814,7 +814,7 @@ public function manage_guest_author_filter_post_data( $post_data, $original_args
 	 *
 	 * @since 3.0
 	 */
-	public function manage_guest_author_save_meta_fields( $post_id, $post ) {
+	public function manage_guest_author_save_meta_fields( $post_id, $post ): void {
 		global $coauthors_plus;
 
 		if ( $post->post_type != $this->post_type ) {
@@ -989,7 +989,7 @@ public function get_guest_author_by( $key, $value, $force = false ) {
 	 * @param   array|string  Optional. An array or string of additional classes. Default null.
 	 * @return  string        The thumbnail image tag, or null if one doesn't exist.
 	 */
-	public function get_guest_author_thumbnail( $guest_author, $size, $class = null ) {
+	public function get_guest_author_thumbnail( $guest_author, $size, $class = null ): ?string {
 		// See if the guest author has an avatar
 		if ( ! has_post_thumbnail( $guest_author->ID ) ) {
 			return null;
@@ -1110,7 +1110,7 @@ public function get_post_meta_key( $key ) {
 	 *
 	 * @return string The generated cache key
 	 */
-	public function get_cache_key( $key, $value ) {
+	public function get_cache_key( $key, $value ): string {
 		// Normalize $key and $value
 		switch ( $key ) {
 			case 'post_name':
@@ -1197,7 +1197,7 @@ public function filter_update_post_metadata( $retnull, $object_id, $meta_key, $m
 	 *
 	 * @param int|object $guest_author The guest author ID or object
 	 */
-	public function delete_guest_author_cache( $id_or_object ) {
+	public function delete_guest_author_cache( $id_or_object ): void {
 
 		if ( is_object( $id_or_object ) ) {
 			$guest_author = $id_or_object;
@@ -1419,7 +1419,7 @@ public function filter_wp_insert_post_empty_content( $maybe_empty, $postarr ) {
 	 * @param object $user_object A WP_User object
 	 * @return array $actions Modified actions
 	 */
-	public function filter_user_row_actions( $actions, $user_object ) {
+	public function filter_user_row_actions( $actions, $user_object ): array {
 
 		if ( ! current_user_can( $this->list_guest_authors_cap ) || is_network_admin() ) {
 			return $actions;
@@ -1474,7 +1474,7 @@ public function filter_get_avatar( $avatar, $id_or_email, $size, $default ) {
 	 *
 	 * @since 3.0
 	 */
-	public function filter_author_link( $link, $author_id, $author_nicename ) {
+	public function filter_author_link( $link, $author_id, $author_nicename ): ?string {
 
 		// If we're using this at the top of the loop on author.php,
 		// our queried object should be set correctly
@@ -1506,7 +1506,7 @@ public function filter_author_link( $link, $author_id, $author_nicename ) {
 	 * @param string $feed Required. Type of feed being generated.
 	 * @return string Feed link for the author.
 	 */
-	public function filter_author_feed_link( $feed_link, $feed ) {
+	public function filter_author_feed_link( $feed_link, $feed ): string {
 		if ( ! is_author() ) {
 			return $feed_link;
 		}
@@ -1559,7 +1559,7 @@ public function filter_personal_data_exporter( $exporters ) {
 	 * @param string $email_address  The guest author email address.
 	 * @return array An array of personal data.
 	 */
-	public function personal_data_exporter( $email_address ) {
+	public function personal_data_exporter( $email_address ): array {
 		$email_address = trim( $email_address );
 
 		$data_to_export = array();
@@ -1643,7 +1643,7 @@ public function personal_data_exporter( $email_address ) {
 	 * @param WP_Post $menu_item The current menu item object.
 	 * @return array
 	 */
-	public function filter_nav_menu_attributes( $atts, $menu_item ) {
+	public function filter_nav_menu_attributes( $atts, $menu_item ): array {
 		if ( ! empty( $menu_item->object ) && 'guest-author' === $menu_item->object ) {
 			$author = $this->get_guest_author_by( 'ID', $menu_item->object_id );
 			if ( ! empty( $author->type ) && $author->type === 'guest-author' ) {
diff --git a/php/class-coauthors-iterator.php b/php/class-coauthors-iterator.php
index 4741afa0..d422cf1e 100644
--- a/php/class-coauthors-iterator.php
+++ b/php/class-coauthors-iterator.php
@@ -34,7 +34,7 @@ public function __construct( $postID = 0 ) {
 		$this->count               = count( $this->authordata_array );
 	}
 
-	public function iterate() {
+	public function iterate(): bool {
 		global $authordata;
 
 		$this->position++;
@@ -63,15 +63,15 @@ public function get_position() {
 		return $this->position === - 1 ? false : $this->position;
 	}
 
-	public function is_last() {
+	public function is_last(): bool {
 		return $this->position === $this->count - 1;
 	}
 
-	public function is_first() {
+	public function is_first(): bool {
 		return $this->position === 0;
 	}
 
-	public function count() {
+	public function count(): int {
 		return $this->count;
 	}
 
diff --git a/php/class-coauthors-plus.php b/php/class-coauthors-plus.php
index fbee12d1..bd234278 100644
--- a/php/class-coauthors-plus.php
+++ b/php/class-coauthors-plus.php
@@ -113,7 +113,7 @@ public function __construct() {
 	 * Register the taxonomy used to managing relationships,
 	 * and the custom post type to store our author data
 	 */
-	public function action_init() {
+	public function action_init(): void {
 
 		// Allow Co-Authors Plus to be easily translated
 		load_plugin_textdomain( 'co-authors-plus', null, dirname( plugin_basename( __FILE__ ) ) . '/languages/' );
@@ -141,7 +141,7 @@ public function action_init() {
 	 * @param WP_Post|int|null $post Post ID or object, null to use global.
 	 * @return bool
 	 */
-	public function is_block_editor( $post = null ) {
+	public function is_block_editor( $post = null ): bool {
 		$screen = get_current_screen();
 
 		// Pre-5.0 compatibility
@@ -156,7 +156,7 @@ public function is_block_editor( $post = null ) {
 	 * When filter is set to enable block editor integration, enqueue assets
 	 * for posts and users where Co Authors is enabled
 	 */
-	public function enqueue_sidebar_plugin_assets() {
+	public function enqueue_sidebar_plugin_assets(): void {
 		if ( $this->is_post_type_enabled() && $this->current_user_can_set_authors() ) {
 			$asset = require dirname( COAUTHORS_PLUS_FILE ) . '/build/index.asset.php';
 
@@ -188,7 +188,7 @@ public function enqueue_sidebar_plugin_assets() {
 	/**
 	 * Register the 'author' taxonomy and add post type support
 	 */
-	public function action_init_late() {
+	public function action_init_late(): void {
 
 		// Register new taxonomy so that we can store all the relationships.
 		$args = array(
@@ -220,7 +220,7 @@ public function action_init_late() {
 	/**
 	 * Initialize the plugin for the admin
 	 */
-	public function admin_init() {
+	public function admin_init(): void {
 		global $pagenow;
 
 		// Add the main JS script and CSS file
@@ -254,7 +254,7 @@ public function admin_init() {
 	 *
 	 * @return array Supported post types.
 	 */
-	public function supported_post_types() {
+	public function supported_post_types(): array {
 		$post_types = array_values( get_post_types() );
 
 		$excluded_built_in = array(
@@ -293,7 +293,7 @@ public function supported_post_types() {
 	 *
 	 * @return bool
 	 */
-	public function is_guest_authors_enabled() {
+	public function is_guest_authors_enabled(): bool {
 		return apply_filters( 'coauthors_guest_authors_enabled', true );
 	}
 
@@ -363,7 +363,7 @@ public function get_coauthor_by( $key, $value, $force = false ) {
 	 * @param string $post_type The name of the post type we're considering
 	 * @return bool Whether co-authors are enabled for the post type.
 	 */
-	public function is_post_type_enabled( $post_type = null ) {
+	public function is_post_type_enabled( $post_type = null ): bool {
 
 		if ( ! $post_type ) {
 			$post_type = get_post_type();
@@ -379,7 +379,7 @@ public function is_post_type_enabled( $post_type = null ) {
 	 * Removes the standard WordPress 'Author' box.
 	 * We don't need it because the Co-Authors Plus one is way cooler.
 	 */
-	public function remove_authors_box() {
+	public function remove_authors_box(): void {
 
 		if ( $this->is_post_type_enabled() ) {
 			remove_meta_box( $this->coreauthors_meta_box_name, get_post_type(), 'normal' );
@@ -389,7 +389,7 @@ public function remove_authors_box() {
 	/**
 	 * Adds a custom 'Authors' box
 	 */
-	public function add_coauthors_box() {
+	public function add_coauthors_box(): void {
 		if ( $this->is_post_type_enabled() && $this->current_user_can_set_authors() ) {
 			if ( false === $this->is_block_editor() ) {
 				add_meta_box( $this->coauthors_meta_box_name, apply_filters( 'coauthors_meta_box_title', __( 'Authors', 'co-authors-plus' ) ), array( $this, 'coauthors_meta_box' ), get_post_type(), apply_filters( 'coauthors_meta_box_context', 'side' ), apply_filters( 'coauthors_meta_box_priority', 'high' ) );
@@ -400,7 +400,7 @@ public function add_coauthors_box() {
 	/**
 	 * Callback for adding the custom 'Authors' box
 	 */
-	public function coauthors_meta_box( $post ) {
+	public function coauthors_meta_box( $post ): void {
 		global $post, $coauthors_plus, $current_screen;
 
 		$post_id = $post->ID;
@@ -480,7 +480,7 @@ public function coauthors_meta_box( $post ) {
 	/**
 	 * Filters the Heartbeat response to refresh the coauthors-nonce
 	 */
-	public function refresh_coauthors_nonce( $response ) {
+	public function refresh_coauthors_nonce( $response ): array {
 		$response['wp-refresh-post-nonces']['replace']['coauthors-nonce']  = wp_create_nonce( 'coauthors-edit' );
 
 		return $response;
@@ -489,7 +489,7 @@ public function refresh_coauthors_nonce( $response ) {
 	/**
 	 * Removes the default 'author' dropdown from quick edit
 	 */
-	public function remove_quick_edit_authors_box() {
+	public function remove_quick_edit_authors_box(): void {
 		global $pagenow;
 
 		if ( 'edit.php' === $pagenow && $this->is_post_type_enabled() ) {
@@ -527,7 +527,7 @@ public function _filter_manage_posts_columns( $posts_columns ) {
 	 *
 	 * @param string $column_name
 	 */
-	public function _filter_manage_posts_custom_column( $column_name ) {
+	public function _filter_manage_posts_custom_column( $column_name ): void {
 		if ( 'coauthors' === $column_name ) {
 			global $post;
 			$authors = get_coauthors( $post->ID );
@@ -558,7 +558,7 @@ public function _filter_manage_posts_custom_column( $column_name ) {
 	/**
 	 * Unset the post count column because it's going to be inaccurate and provide our own
 	 */
-	public function _filter_manage_users_columns( $columns ) {
+	public function _filter_manage_users_columns( $columns ): array {
 
 		$new_columns = array();
 		// Unset and add our column while retaining the order of the columns
@@ -595,7 +595,7 @@ public function _filter_manage_users_custom_column( $value, $column_name, $user_
 	/**
 	 * Quick Edit co-authors box.
 	 */
-	public function _action_quick_edit_custom_box( $column_name, $post_type ) {
+	public function _action_quick_edit_custom_box( $column_name, $post_type ): void {
 		if ( 'coauthors' !== $column_name || ! $this->is_post_type_enabled( $post_type ) || ! $this->current_user_can_set_authors() ) {
 			return;
 		}
@@ -613,7 +613,7 @@ public function _action_quick_edit_custom_box( $column_name, $post_type ) {
 	/**
 	 * When we update the terms at all, we should update the published post count for each user
 	 */
-	public function _update_users_posts_count( $tt_ids, $taxonomy ) {
+	public function _update_users_posts_count( $tt_ids, $taxonomy ): void {
 		global $wpdb;
 
 		$tt_ids   = implode( ', ', array_map( 'intval', $tt_ids ) );
@@ -739,7 +739,7 @@ public function posts_join_filter( $join, $query ) {
 	 *
 	 * @return string
 	 */
-	public function posts_where_filter( $where, $query ) {
+	public function posts_where_filter( $where, $query ): string {
 		global $wpdb;
 
 		if ( $query->is_author() ) {
@@ -918,7 +918,7 @@ public function coauthors_set_post_author_field( $data, $postarr ) {
 	 *
 	 * @param $post_ID
 	 */
-	public function coauthors_update_post( $post_id, $post ) {
+	public function coauthors_update_post( $post_id, $post ): void {
 
 		if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) {
 			return;
@@ -948,7 +948,7 @@ public function coauthors_update_post( $post_id, $post ) {
 		}
 	}
 
-	public function has_author_terms( $post_id ) {
+	public function has_author_terms( $post_id ): bool {
 		$terms = wp_get_object_terms( $post_id, $this->coauthor_taxonomy, array( 'fields' => 'ids' ) );
 		return ! empty( $terms ) && ! is_wp_error( $terms );
 	}
@@ -961,7 +961,7 @@ public function has_author_terms( $post_id ) {
 	 * @param bool
 	 * @param string
 	 */
-	public function add_coauthors( $post_id, $coauthors, $append = false, $query_type = 'user_nicename' ) {
+	public function add_coauthors( $post_id, $coauthors, $append = false, $query_type = 'user_nicename' ): bool {
 		global $current_user, $wpdb;
 
 		$post_id = (int) $post_id;
@@ -1030,7 +1030,7 @@ public function add_coauthors( $post_id, $coauthors, $append = false, $query_typ
 	 *
 	 * @param delete_id
 	 */
-	public function delete_user_action( $delete_id ) {
+	public function delete_user_action( $delete_id ): void {
 		global $wpdb;
 
 		$reassign_id = isset( $_POST['reassign_user'] ) ? absint( $_POST['reassign_user'] ) : false; // phpcs:ignore
@@ -1124,7 +1124,7 @@ public function filter_wp_get_object_terms( $terms, $object_ids, $taxonomies, $a
 	 * @param int $user_id WP user ID
 	 * @return int Post count
 	 */
-	public function filter_count_user_posts( $count, $user_id ) {
+	public function filter_count_user_posts( $count, $user_id ): int {
 		$user     = get_userdata( $user_id );
 		$coauthor = $this->get_coauthor_by( 'user_nicename', $user->user_nicename );
 
@@ -1185,7 +1185,7 @@ public function current_user_can_set_authors() {
 	 * @param string $selection The assembled selection query
 	 * @void
 	 */
-	public function fix_author_page( $selection ) {
+	public function fix_author_page( $selection ): void {
 
 		global $wp_query, $authordata;
 
@@ -1231,7 +1231,7 @@ public function fix_author_page( $selection ) {
 	 * @param  array $settings The existing IS settings to filter
 	 * @return array           The filtered IS settings
 	 */
-	public function filter_infinite_scroll_js_settings( $settings ) {
+	public function filter_infinite_scroll_js_settings( $settings ): array {
 		if ( ! is_author() ) {
 			return $settings;
 		}
@@ -1250,7 +1250,7 @@ public function filter_infinite_scroll_js_settings( $settings ) {
 	/**
 	 * Main function that handles search-as-you-type for adding co-authors
 	 */
-	public function ajax_suggest() {
+	public function ajax_suggest(): void {
 
 		if ( ! isset( $_REQUEST['_wpnonce'] ) || ! wp_verify_nonce( $_REQUEST['_wpnonce'], 'coauthors-search' ) ) {
 			die();
@@ -1296,7 +1296,7 @@ public function ajax_suggest() {
 	/**
 	 * Get matching co-authors based on a search value
 	 */
-	public function search_authors( $search = '', $ignored_authors = array() ) {
+	public function search_authors( $search = '', $ignored_authors = array() ): array {
 
 		// Since 2.7, we're searching against the term description for the fields
 		// instead of the user details. If the term is missing, we probably need to
@@ -1379,7 +1379,7 @@ public function filter_terms_clauses( $pieces ) {
 	/**
 	 * Functions to add scripts and css
 	 */
-	public function enqueue_scripts( $hook_suffix ) {
+	public function enqueue_scripts( $hook_suffix ): void {
 		global $pagenow, $post;
 
 		if ( ! $this->is_valid_page() || ! $this->is_post_type_enabled() || ! $this->current_user_can_set_authors() ) {
@@ -1406,7 +1406,7 @@ public function enqueue_scripts( $hook_suffix ) {
 	/**
 	 * load-edit.php is when the screen has been set up
 	 */
-	public function load_edit() {
+	public function load_edit(): void {
 
 		$screen = get_current_screen();
 		if ( in_array( $screen->post_type, $this->supported_post_types() ) ) {
@@ -1449,7 +1449,7 @@ public function filter_views( $views ) {
 	/**
 	 * Adds necessary javascript variables to admin pages
 	 */
-	public function js_vars() {
+	public function js_vars(): void {
 
 		if ( ! $this->is_valid_page() || ! $this->is_post_type_enabled() || ! $this->current_user_can_set_authors() ) {
 			return;
@@ -1479,7 +1479,7 @@ public function js_vars() {
 	 *
 	 * @return bool
 	 */
-	public function is_valid_page() {
+	public function is_valid_page(): bool {
 		global $pagenow;
 
 		return in_array( $pagenow, $this->_pages_whitelist );
@@ -1494,7 +1494,7 @@ public function is_valid_page() {
 	 *
 	 * @return array caps that CAP should filter
 	 */
-	public function get_to_be_filtered_caps() {
+	public function get_to_be_filtered_caps(): array {
 		if ( ! empty( $this->supported_post_types() ) && empty( $this->to_be_filtered_caps ) ) {
 			$this->to_be_filtered_caps[] = 'edit_post'; // Need to filter this too, unfortunately: http://core.trac.wordpress.org/ticket/22415
 			$this->to_be_filtered_caps[] = 'read_post';
@@ -1637,7 +1637,7 @@ public function update_author_term( $coauthor ) {
 	 * @param int   $post_id
 	 * @return array
 	 */
-	public function filter_ef_calendar_item_information_fields( $information_fields, $post_id ) {
+	public function filter_ef_calendar_item_information_fields( $information_fields, $post_id ): array {
 
 		// Don't add the author row again if another plugin has removed
 		if ( ! array_key_exists( $this->coauthor_taxonomy, $information_fields ) ) {
@@ -1666,7 +1666,7 @@ public function filter_ef_calendar_item_information_fields( $information_fields,
 	 * @param object $parent_term
 	 * @return string
 	 */
-	public function filter_ef_story_budget_term_column_value( $column_name, $post, $parent_term ) {
+	public function filter_ef_story_budget_term_column_value( $column_name, $post, $parent_term ): string {
 
 		// We only want to modify the 'author' column
 		if ( $this->coauthor_taxonomy != $column_name ) {
@@ -1690,7 +1690,7 @@ public function filter_ef_story_budget_term_column_value( $column_name, $post, $
 	 * @param array $image_dimensions Required. Dimensions for images used.
 	 * @return array Open Graph Tags either as they were passed or updated.
 	 */
-	public function filter_jetpack_open_graph_tags( $og_tags, $image_dimensions ) {
+	public function filter_jetpack_open_graph_tags( $og_tags, $image_dimensions ): array {
 
 		if ( is_author() ) {
 			$author = get_queried_object();
@@ -1728,7 +1728,7 @@ public function filter_jetpack_open_graph_tags( $og_tags, $image_dimensions ) {
 	 * @param int $post_id ID of the post for which to retrieve co-authors.
 	 * @return array Array of co-author WP_Term objects.
 	 */
-	public function get_coauthor_terms_for_post( $post_id ) {
+	public function get_coauthor_terms_for_post( $post_id ): array {
 
 		if ( ! $post_id ) {
 			return array();
@@ -1764,7 +1764,7 @@ public function get_coauthor_terms_for_post( $post_id ) {
 	 *
 	 * @param $post_id The Post ID.
 	 */
-	public function clear_cache( $post_id ) {
+	public function clear_cache( $post_id ): void {
 		wp_cache_delete( 'coauthors_post_' . $post_id, 'co-authors-plus' );
 	}
 
@@ -1773,7 +1773,7 @@ public function clear_cache( $post_id ) {
 	 *
 	 * @param $post_id The Post ID.
 	 */
-	public function clear_cache_on_terms_set( $object_id, $terms, $tt_ids, $taxonomy, $append, $old_tt_ids ) {
+	public function clear_cache_on_terms_set( $object_id, $terms, $tt_ids, $taxonomy, $append, $old_tt_ids ): void {
 
 		// We only care about the co-authors taxonomy.
 		if ( $this->coauthor_taxonomy !== $taxonomy ) {
@@ -1791,7 +1791,7 @@ public function clear_cache_on_terms_set( $object_id, $terms, $tt_ids, $taxonomy
 	 *
 	 * @return string Archive Page Title
 	 */
-	public function filter_author_archive_title( $title ) {
+	public function filter_author_archive_title( $title ): string {
 
 		// Bail if not an author archive template
 		if ( ! is_author() ) {
@@ -1811,7 +1811,7 @@ public function filter_author_archive_title( $title ) {
 	 * @param object $guest_author guest-author object.
 	 * @return int post count for the guest author
 	 */
-	public function get_guest_author_post_count( $guest_author ) {
+	public function get_guest_author_post_count( $guest_author ): int {
 		if ( ! is_object( $guest_author ) ) {
 			return 0;
 		}
@@ -1839,9 +1839,9 @@ public function get_guest_author_post_count( $guest_author ) {
 	 * @param $url string Avatar URL
 	 * @param $id  int Author ID
 	 *
-	 * @return string Avatar URL
+	 * @return array Avatar URL
 	 */
-	public function filter_pre_get_avatar_data_url( $args, $id ) {
+	public function filter_pre_get_avatar_data_url( $args, $id ): array {
 		global $wp_current_filter;
 
 		if ( isset( $args['url'] ) || ! $id || ! is_numeric( $id ) || ! $this->is_guest_authors_enabled() ) {
@@ -1888,7 +1888,7 @@ public function filter_pre_get_avatar_data_url( $args, $id ) {
 	 * @param WP_REST_Response $response Response for an individual author taxonomy term.
 	 * @return WP_REST_Response $response Same response, possibly mutated to eliminate value of description.
 	 */
-	public function conditionally_hide_author_term_description( WP_REST_Response $response ) {
+	public function conditionally_hide_author_term_description( WP_REST_Response $response ): \WP_REST_Response {
 		$capability = apply_filters(
 			'coauthors_rest_view_description_cap',
 			'edit_posts'
diff --git a/php/class-coauthors-template-filters.php b/php/class-coauthors-template-filters.php
index 7ac1ab95..0db4e845 100644
--- a/php/class-coauthors-template-filters.php
+++ b/php/class-coauthors-template-filters.php
@@ -15,11 +15,11 @@ public function __construct() {
 		add_action( 'rss2_item', array( $this, 'action_add_rss_guest_authors' ) );
 	}
 
-	public function filter_the_author() {
+	public function filter_the_author(): string {
 		return coauthors( null, null, null, null, false );
 	}
 
-	public function filter_the_author_posts_link() {
+	public function filter_the_author_posts_link(): string {
 		return coauthors_posts_links( null, null, null, null, false );
 	}
 
@@ -36,7 +36,7 @@ public function filter_the_author_rss( $the_author ) {
 		return $the_author;
 	}
 
-	public function action_add_rss_guest_authors() {
+	public function action_add_rss_guest_authors(): void {
 		$coauthors = get_coauthors();
 
 		// remove the first guest author who is added to the first dc:creator element
diff --git a/php/class-coauthors-wp-list-table.php b/php/class-coauthors-wp-list-table.php
index d0f8912e..ed22a2a0 100755
--- a/php/class-coauthors-wp-list-table.php
+++ b/php/class-coauthors-wp-list-table.php
@@ -215,7 +215,7 @@ public function column_default( $item, $column_name ) {
 	/**
 	 * Render display name, e.g. author name
 	 */
-	public function column_display_name( $item ) {
+	public function column_display_name( $item ): string {
 
 		$item_edit_link   = get_edit_post_link( $item->ID );
 		$args             = array(
@@ -251,7 +251,7 @@ public function column_display_name( $item ) {
 	/**
 	 * Render linked account
 	 */
-	public function column_linked_account( $item ) {
+	public function column_linked_account( $item ): string {
 		if ( $item->linked_account ) {
 			$account = get_user_by( 'login', $item->linked_account );
 			if ( $account ) {
@@ -267,7 +267,7 @@ public function column_linked_account( $item ) {
 	/**
 	 * Render the published post count column
 	 */
-	public function column_posts( $item ) {
+	public function column_posts( $item ): string {
 		global $coauthors_plus;
 		$count = $coauthors_plus->get_guest_author_post_count( $item );
 
diff --git a/php/class-wp-cli.php b/php/class-wp-cli.php
index a1fab6aa..69f8390c 100644
--- a/php/class-wp-cli.php
+++ b/php/class-wp-cli.php
@@ -19,7 +19,7 @@ class CoAuthorsPlus_Command extends WP_CLI_Command {
 	 *
 	 * @subcommand create-guest-authors
 	 */
-	public function create_guest_authors( $args, $assoc_args ) {
+	public function create_guest_authors( $args, $assoc_args ): void {
 		global $coauthors_plus;
 
 		$defaults = array(
@@ -52,7 +52,7 @@ public function create_guest_authors( $args, $assoc_args ) {
 	 *
 	 * @subcommand create-terms-for-posts
 	 */
-	public function create_terms_for_posts() {
+	public function create_terms_for_posts(): void {
 		global $coauthors_plus, $wp_post_types;
 
 		// Cache these to prevent repeated lookups
@@ -125,7 +125,7 @@ public function create_terms_for_posts() {
 	 * @subcommand assign-coauthors
 	 * @synopsis [--meta_key=<key>] [--post_type=<ptype>] [--append_coauthors]
 	 */
-	public function assign_coauthors( $args, $assoc_args ) {
+	public function assign_coauthors( $args, $assoc_args ): void {
 		global $coauthors_plus;
 
 		$defaults   = array(
@@ -215,7 +215,7 @@ public function assign_coauthors( $args, $assoc_args ) {
 	 * @subcommand assign-user-to-coauthor
 	 * @synopsis --user_login=<user-login> --coauthor=<co-author>
 	 */
-	public function assign_user_to_coauthor( $args, $assoc_args ) {
+	public function assign_user_to_coauthor( $args, $assoc_args ): void {
 		global $coauthors_plus, $wpdb;
 
 		$defaults   = array(
@@ -290,7 +290,7 @@ public function assign_user_to_coauthor( $args, $assoc_args ) {
 	 * @subcommand reassign-terms
 	 * @synopsis [--author-mapping=<file>] [--old_term=<slug>] [--new_term=<slug>]
 	 */
-	public function reassign_terms( $args, $assoc_args ) {
+	public function reassign_terms( $args, $assoc_args ): void {
 		global $coauthors_plus;
 
 		$defaults   = array(
@@ -382,7 +382,7 @@ public function reassign_terms( $args, $assoc_args ) {
 	 * @subcommand rename-coauthor
 	 * @synopsis --from=<user-login> --to=<user-login>
 	 */
-	public function rename_coauthor( $args, $assoc_args ) {
+	public function rename_coauthor( $args, $assoc_args ): void {
 		global $coauthors_plus, $wpdb;
 
 		$defaults   = array(
@@ -434,7 +434,7 @@ public function rename_coauthor( $args, $assoc_args ) {
 	 * @subcommand swap-coauthors
 	 * @synopsis --from=<user-login> --to=<user-login> [--post_type=<ptype>] [--dry=<dry>]
 	 */
-	public function swap_coauthors( $args, $assoc_args ) {
+	public function swap_coauthors( $args, $assoc_args ): void {
 		global $coauthors_plus, $wpdb;
 
 		$defaults = array(
@@ -550,7 +550,7 @@ public function swap_coauthors( $args, $assoc_args ) {
 	 * @subcommand list-posts-without-terms
 	 * @synopsis [--post_type=<ptype>]
 	 */
-	public function list_posts_without_terms( $args, $assoc_args ) {
+	public function list_posts_without_terms( $args, $assoc_args ): void {
 		global $coauthors_plus;
 
 		$defaults   = array(
@@ -599,7 +599,7 @@ public function list_posts_without_terms( $args, $assoc_args ) {
 	 *
 	 * @subcommand migrate-author-terms
 	 */
-	public function migrate_author_terms( $args, $assoc_args ) {
+	public function migrate_author_terms( $args, $assoc_args ): void {
 		global $coauthors_plus;
 
 		$author_terms = get_terms( $coauthors_plus->coauthor_taxonomy, array( 'hide_empty' => false ) );
@@ -637,7 +637,7 @@ public function migrate_author_terms( $args, $assoc_args ) {
 	 *
 	 * @subcommand update-author-terms
 	 */
-	public function update_author_terms() {
+	public function update_author_terms(): void {
 		global $coauthors_plus;
 		$author_terms = get_terms( $coauthors_plus->coauthor_taxonomy, array( 'hide_empty' => false ) );
 		WP_CLI::line( 'Now updating ' . count( $author_terms ) . ' terms' );
@@ -712,7 +712,7 @@ public function update_author_terms() {
 	 *
 	 * @subcommand remove-terms-from-revisions
 	 */
-	public function remove_terms_from_revisions() {
+	public function remove_terms_from_revisions(): void {
 		global $wpdb;
 
 		$ids = $wpdb->get_col( "SELECT ID FROM $wpdb->posts WHERE post_type='revision' AND post_status='inherit'" );
@@ -739,7 +739,7 @@ public function remove_terms_from_revisions() {
 	 * @subcommand create-guest-authors-from-wxr
 	 * @synopsis --file=<file>
 	 */
-	public function create_guest_authors_from_wxr( $args, $assoc_args ) {
+	public function create_guest_authors_from_wxr( $args, $assoc_args ): void {
 		global $coauthors_plus;
 
 		$defaults   = array(
@@ -798,7 +798,7 @@ public function create_guest_authors_from_wxr( $args, $assoc_args ) {
 	 * [--user_email=<user_email>]
 	 * [--description=<description>]
 	 */
-	public function create_author( $args, $assoc_args ) {
+	public function create_author( $args, $assoc_args ): void {
 		$this->create_guest_author( $assoc_args );
 	}
 
@@ -808,7 +808,7 @@ public function create_author( $args, $assoc_args ) {
 	 * @subcommand create-guest-authors-from-csv
 	 * @synopsis --file=<file>
 	 */
-	public function create_guest_authors_from_csv( $args, $assoc_args ) {
+	public function create_guest_authors_from_csv( $args, $assoc_args ): void {
 		global $coauthors_plus;
 
 		$defaults   = array(
@@ -889,7 +889,7 @@ public function create_guest_authors_from_csv( $args, $assoc_args ) {
 	 * @param $author array author args. Required: display_name, user_login
 	 * @return void
 	 */
-	private function create_guest_author( $author ) {
+	private function create_guest_author( $author ): void {
 		global $coauthors_plus;
 		$guest_author = $coauthors_plus->guest_authors->get_guest_author_by( 'user_email', $author['user_email'], true );
 
@@ -899,7 +899,8 @@ private function create_guest_author( $author ) {
 
 		if ( $guest_author ) {
 			/* translators: Guest Author ID. */
-			return WP_CLI::warning( sprintf( esc_html__( '-- Author already exists (ID #%s); skipping.', 'co-authors-plus' ), $guest_author->ID ) );
+			WP_CLI::warning( sprintf( esc_html__( '-- Author already exists (ID #%s); skipping.', 'co-authors-plus' ), $guest_author->ID ) );
+			return;
 		}
 
 		WP_CLI::line( esc_html__( '-- Not found; creating profile.', 'co-authors-plus' ) );
@@ -919,7 +920,8 @@ private function create_guest_author( $author ) {
 
 		if ( is_wp_error( $guest_author_id ) ) {
 			/* translators: The error message. */
-			return WP_CLI::warning( sprintf( esc_html__( '-- Failed to create guest author: %s', 'co-authors-plus' ), $guest_author_id->get_error_message() ) );
+			WP_CLI::warning( sprintf( esc_html__( '-- Failed to create guest author: %s', 'co-authors-plus' ), $guest_author_id->get_error_message() ) );
+			return;
 		}
 
 		if ( isset( $author['author_id'] ) ) {
@@ -935,7 +937,7 @@ private function create_guest_author( $author ) {
 	/**
 	 * Clear all the caches for memory management.
 	 */
-	private function stop_the_insanity() {
+	private function stop_the_insanity(): void {
 		global $wpdb, $wp_object_cache;
 
 		$wpdb->queries = array(); // or define( 'WP_IMPORTING', true );
diff --git a/php/integrations/yoast.php b/php/integrations/yoast.php
index 9c4f4ab1..a580823a 100644
--- a/php/integrations/yoast.php
+++ b/php/integrations/yoast.php
@@ -29,7 +29,7 @@ class Yoast {
 	 *
 	 * @return void
 	 */
-	public static function init() {
+	public static function init(): void {
 		add_action( 'plugins_loaded', [ __CLASS__, 'do_initialization' ] );
 	}
 
@@ -38,7 +38,7 @@ public static function init() {
 	 *
 	 * @return void
 	 */
-	public static function do_initialization() {
+	public static function do_initialization(): void {
 		if ( self::should_initialize() ) {
 			require_once __DIR__ . '/yoast/class-coauthor.php';
 			self::register_hooks();
@@ -50,7 +50,7 @@ public static function do_initialization() {
 	 *
 	 * @return boolean
 	 */
-	protected static function should_initialize() {
+	protected static function should_initialize(): bool {
 		return self::is_yoast_active() && ! self::is_yoast_legacy_integration_enabled();
 	}
 
@@ -59,7 +59,7 @@ protected static function should_initialize() {
 	 *
 	 * @return boolean
 	 */
-	protected static function is_yoast_active() {
+	protected static function is_yoast_active(): bool {
 		return defined( 'WPSEO_VERSION' ) && version_compare( WPSEO_VERSION, self::YOAST_MIN_VERSION, '>=' );
 	}
 
@@ -70,7 +70,7 @@ protected static function is_yoast_active() {
 	 *
 	 * @return boolean
 	 */
-	protected static function is_yoast_legacy_integration_enabled() {
+	protected static function is_yoast_legacy_integration_enabled(): bool {
 		return defined( 'YOAST_SEO_COAUTHORS_PLUS' ) && YOAST_SEO_COAUTHORS_PLUS;
 	}
 
@@ -79,7 +79,7 @@ protected static function is_yoast_legacy_integration_enabled() {
 	 *
 	 * @return void
 	 */
-	public static function register_hooks() {
+	public static function register_hooks(): void {
 		add_filter( 'wpseo_schema_graph', [ __CLASS__, 'filter_graph' ], 11, 2 );
 		add_filter( 'wpseo_schema_author', [ __CLASS__, 'filter_author_graph' ], 11, 4 );
 		add_filter( 'wpseo_schema_profilepage', [ __CLASS__, 'filter_schema_profilepage' ], 11, 4 );
@@ -99,7 +99,7 @@ public static function register_hooks() {
 	 *
 	 * @return array The (potentially altered) schema graph.
 	 */
-	public static function filter_schema_profilepage( $data, $context, $graph_piece_generator, $graph_piece_generators ) {
+	public static function filter_schema_profilepage( $data, $context, $graph_piece_generator, $graph_piece_generators ): array {
 
 		if ( ! is_author() ) {
 			return $data;
@@ -129,7 +129,7 @@ public static function filter_schema_profilepage( $data, $context, $graph_piece_
 	 *
 	 * @return array The (potentially altered) schema graph.
 	 */
-	public static function filter_author_graph( $data, $context, $graph_piece_generator, $graph_piece_generators ) {
+	public static function filter_author_graph( $data, $context, $graph_piece_generator, $graph_piece_generators ): array {
 		if ( ! isset( $data['image']['url'] ) ) {
 			return $data;
 		}
@@ -153,7 +153,7 @@ public static function filter_author_graph( $data, $context, $graph_piece_genera
 	 *
 	 * @return array The (potentially altered) schema graph.
 	 */
-	public static function filter_graph( $data, $context ) {
+	public static function filter_graph( $data, $context ): array {
 		if ( ! is_singular() ) {
 			return $data;
 		}
@@ -228,7 +228,7 @@ function( $piece ) {
 	 * @param Indexable_Presentation $presentation The presentation of an indexable.
 	 * @return string
 	 */
-	public static function filter_author_meta( $author_name, $presentation ) {
+	public static function filter_author_meta( $author_name, $presentation ): string {
 		$author_objects = get_coauthors( $presentation->context->post->id );
 
 		// Fallback in case of error.
@@ -246,7 +246,7 @@ public static function filter_author_meta( $author_name, $presentation ) {
 	 * @param Indexable_Presentation $presentation The presentation of an indexable.
 	 * @return array The potentially amended enhanced Slack sharing data.
 	 */
-	public static function filter_slack_data( $data, $presentation ) {
+	public static function filter_slack_data( $data, $presentation ): array {
 		$author_objects = get_coauthors( $presentation->context->post->id );
 
 		// Fallback in case of error.
@@ -265,7 +265,7 @@ public static function filter_slack_data( $data, $presentation ) {
 	 * @param WP_User[] $author_objects The list of authors.
 	 * @return string Author display names separated by commas.
 	 */
-	private static function get_authors_display_names_output( $author_objects ) {
+	private static function get_authors_display_names_output( $author_objects ): string {
 		$output = '';
 		foreach ( $author_objects as $i => $author ) {
 			$output .= $author->display_name;
diff --git a/php/integrations/yoast/class-coauthor.php b/php/integrations/yoast/class-coauthor.php
index 7ce940b0..ebd3375a 100644
--- a/php/integrations/yoast/class-coauthor.php
+++ b/php/integrations/yoast/class-coauthor.php
@@ -25,7 +25,7 @@ class CoAuthor extends Author {
 	 *
 	 * @return bool
 	 */
-	public function is_needed() {
+	public function is_needed(): bool {
 		return true;
 	}
 
@@ -104,7 +104,7 @@ protected function determine_user_id() {
 	 *
 	 * @return array An array of Schema Person data.
 	 */
-	protected function build_person_data_for_guest_author( $guest_author, $add_hash = false ) {
+	protected function build_person_data_for_guest_author( $guest_author, $add_hash = false ): array {
 		$schema_id = $this->context->site_url . Schema_IDs::PERSON_LOGO_HASH;
 		$data      = [
 			'@type' => $this->type,
@@ -143,7 +143,7 @@ protected function build_person_data_for_guest_author( $guest_author, $add_hash
 	 *
 	 * @return array The Person schema data.
 	 */
-	protected function add_guest_author_same_as_urls( $data, $guest_author ) {
+	protected function add_guest_author_same_as_urls( $data, $guest_author ): array {
 		$same_as_urls = [];
 
 		// Add the "Website" field from co-authors' contact info.
diff --git a/tests/Behat/FeatureContext.php b/tests/Behat/FeatureContext.php
index e79421ff..be0d5e3b 100644
--- a/tests/Behat/FeatureContext.php
+++ b/tests/Behat/FeatureContext.php
@@ -25,7 +25,7 @@ final class FeatureContext extends WP_CLI_FeatureContext {
 	 * Adapted from https://github.com/wearerequired/traduttore/blob/master/tests/phpunit/tests/Behat/FeatureContext.php
 	 * with credit and thanks to them.
 	 */
-	public function given_a_wp_installation_with_the_cap_plugin() {
+	public function given_a_wp_installation_with_the_cap_plugin(): void {
 		$this->install_wp();
 
 		// Symlink the current project folder into the WP folder as a plugin.
@@ -46,7 +46,7 @@ public function given_a_wp_installation_with_the_cap_plugin() {
 	 * @param string $directory Directory to ensure the existence of.
 	 * @throws \RuntimeException Directory could not be created.
 	 */
-	private function ensure_dir_exists( $directory ) {
+	private function ensure_dir_exists( $directory ): void {
 		$parent = dirname( $directory );
 
 		if ( ! empty( $parent ) && ! is_dir( $parent ) ) {
@@ -65,7 +65,7 @@ private function ensure_dir_exists( $directory ) {
 	 *
 	 * @param string $post_name Post name to use.
 	 */
-	public function there_is_a_published_post( $post_name ) {
+	public function there_is_a_published_post( $post_name ): void {
 		$this->proc( "wp post create --post_title='{$post_name}' --post_name='{$post_name}' --post_status='publish'" )->run_check();
 	}
 }
diff --git a/tests/Integration/AuthorQueriedObjectTest.php b/tests/Integration/AuthorQueriedObjectTest.php
index 77c68d2d..223f59fe 100644
--- a/tests/Integration/AuthorQueriedObjectTest.php
+++ b/tests/Integration/AuthorQueriedObjectTest.php
@@ -16,7 +16,7 @@ class AuthorQueriedObjectTest extends TestCase {
 	 *
 	 * @group ms-required
 	 */
-	public function test__author_queried_object_fix() {
+	public function test__author_queried_object_fix(): void {
 
 		global $wp_rewrite, $coauthors_plus;
 
@@ -91,7 +91,7 @@ public function test__author_queried_object_fix() {
 	 *
 	 * @group ms-required
 	 */
-	public function test__author_non_existent_page_throws_404() {
+	public function test__author_non_existent_page_throws_404(): void {
 		global $wp_rewrite;
 
 		/**
diff --git a/tests/Integration/AuthorQueriesTest.php b/tests/Integration/AuthorQueriesTest.php
index 74aa5a00..35d30b23 100644
--- a/tests/Integration/AuthorQueriesTest.php
+++ b/tests/Integration/AuthorQueriesTest.php
@@ -8,7 +8,7 @@ class AuthorQueriesTest extends TestCase {
 	 * Test a simple query that a post is returned after setting a co-author on it.
 	 * The focus is the query by user login instead of ID.
 	 */
-	public function test_get_post_by_user_login_when_single_author_is_set_as_post_author() {
+	public function test_get_post_by_user_login_when_single_author_is_set_as_post_author(): void {
 		$author = $this->create_author();
 		$post   = $this->create_post( $author );
 		$this->_cap->add_coauthors( $post->ID, array( $author->user_login ) );
@@ -27,7 +27,7 @@ public function test_get_post_by_user_login_when_single_author_is_set_as_post_au
 	 * Test a simple query that a post is returned after setting a co-author on it.
 	 * This test is run as the default administrator user.
 	 */
-	public function test_get_post_by_user_ID_when_single_author_is_set_as_post_author_but_current_user_is_admin() {
+	public function test_get_post_by_user_ID_when_single_author_is_set_as_post_author_but_current_user_is_admin(): void {
 		$author = $this->create_author();
 		$post   = $this->create_post( $author );
 		$this->_cap->add_coauthors( $post->ID, array( $author->user_login ) );
@@ -46,7 +46,7 @@ public function test_get_post_by_user_ID_when_single_author_is_set_as_post_autho
 	 * Test a simple query that a post is returned after setting a co-author on it.
 	 * This test is run as the author user. This is to ensure that the logic works for non-administrator roles. See #508.
 	 */
-	public function test_get_post_by_user_ID_when_single_author_is_set_as_post_author_but_current_user_is_author() {
+	public function test_get_post_by_user_ID_when_single_author_is_set_as_post_author_but_current_user_is_author(): void {
 		$author = $this->create_author();
 		$post   = $this->create_post( $author );
 		$this->_cap->add_coauthors( $post->ID, array( $author->user_login ) );
@@ -67,7 +67,7 @@ public function test_get_post_by_user_ID_when_single_author_is_set_as_post_autho
 	 * Test a simple user_login query that a post is returned after setting multiple co-authors for it.
 	 * The post_author is set as the first co-author.
 	 */
-	public function test_get_post_by_user_ID_when_queried_author_is_set_as_post_author() {
+	public function test_get_post_by_user_ID_when_queried_author_is_set_as_post_author(): void {
 		$author1 = $this->create_author( 'author1' );
 		$author2 = $this->create_author( 'author2' );
 		$post   = $this->create_post( $author1 );
@@ -88,7 +88,7 @@ public function test_get_post_by_user_ID_when_queried_author_is_set_as_post_auth
 	 * The post_author is set as the first co-author, but we're querying by the second co-author, so
 	 * this is magic working now.
 	 */
-	public function test_get_post_by_user_ID_when_queried_author_is_not_set_as_post_author() {
+	public function test_get_post_by_user_ID_when_queried_author_is_not_set_as_post_author(): void {
 		$author1 = $this->create_author( 'author1' );
 		$author2 = $this->create_author( 'author2' );
 		$post   = $this->create_post( $author1 );
@@ -104,7 +104,7 @@ public function test_get_post_by_user_ID_when_queried_author_is_not_set_as_post_
 		$this->assertEquals( $post->ID, $query->posts[0]->ID );
 	}
 
-	public function test_get_post_by_user_ID_when_queried_author_is_set_as_post_author_but_there_is_a_tag() {
+	public function test_get_post_by_user_ID_when_queried_author_is_set_as_post_author_but_there_is_a_tag(): void {
 		$author = $this->create_author();
 		$post   = $this->create_post( $author );
 		$this->_cap->add_coauthors( $post->ID, array( $author->user_login ) );
@@ -121,7 +121,7 @@ public function test_get_post_by_user_ID_when_queried_author_is_set_as_post_auth
 		$this->assertEquals( $post->ID, $query->posts[0]->ID );
 	}
 
-	public function test_get_post_by_user_ID_when_queried_author_is_not_set_as_post_author_and_there_is_a_tag() {
+	public function test_get_post_by_user_ID_when_queried_author_is_not_set_as_post_author_and_there_is_a_tag(): void {
 		$author1 = $this->create_author( 'author1' );
 		$author2 = $this->create_author( 'author2' );
 		$post   = $this->create_post( $author1 );
diff --git a/tests/Integration/CoAuthorsPlusTest.php b/tests/Integration/CoAuthorsPlusTest.php
index 7468a041..01a78a49 100644
--- a/tests/Integration/CoAuthorsPlusTest.php
+++ b/tests/Integration/CoAuthorsPlusTest.php
@@ -41,7 +41,7 @@ public function set_up() {
 	 *
 	 * @covers CoAuthors_Plus::is_guest_authors_enabled()
 	 */
-	public function test_is_guest_authors_enabled() {
+	public function test_is_guest_authors_enabled(): void {
 
 		global $coauthors_plus;
 
@@ -61,7 +61,7 @@ public function test_is_guest_authors_enabled() {
 	 *
 	 * @covers CoAuthors_Plus::get_coauthor_by()
 	 */
-	public function test_get_coauthor_by_when_guest_author() {
+	public function test_get_coauthor_by_when_guest_author(): void {
 
 		global $coauthors_plus;
 
@@ -85,7 +85,7 @@ public function test_get_coauthor_by_when_guest_author() {
 	 *
 	 * @covers CoAuthors_Plus::get_coauthor_by()
 	 */
-	public function test_get_coauthor_by_when_guest_author_has_unicode_username() {
+	public function test_get_coauthor_by_when_guest_author_has_unicode_username(): void {
 
 		global $coauthors_plus;
 
@@ -110,7 +110,7 @@ public function test_get_coauthor_by_when_guest_author_has_unicode_username() {
 	 *
 	 * @covers CoAuthors_Plus::get_coauthor_by()
 	 */
-	public function test_get_coauthor_by_when_guest_authors_not_enabled() {
+	public function test_get_coauthor_by_when_guest_authors_not_enabled(): void {
 
 		global $coauthors_plus;
 
@@ -159,7 +159,7 @@ public function test_get_coauthor_by_when_guest_authors_not_enabled() {
 	 *
 	 * @covers CoAuthors_Plus::is_post_type_enabled()
 	 */
-	public function test_is_post_type_enabled() {
+	public function test_is_post_type_enabled(): void {
 
 		global $coauthors_plus, $post;
 
@@ -204,7 +204,7 @@ public function test_is_post_type_enabled() {
 	 *
 	 * @covers CoAuthors_Plus::current_user_can_set_authors()
 	 */
-	public function test_current_user_can_set_author() {
+	public function test_current_user_can_set_author(): void {
 		global $coauthors_plus;
 
 		$this->assertFalse( $coauthors_plus->current_user_can_set_authors() );
@@ -242,7 +242,7 @@ public function test_current_user_can_set_author() {
 	 *
 	 * @covers CoAuthors_Plus::current_user_can_set_authors()
 	 */
-	public function test_current_user_can_set_authors_using_coauthors_plus_edit_authors_filter() {
+	public function test_current_user_can_set_authors_using_coauthors_plus_edit_authors_filter(): void {
 
 		global $coauthors_plus;
 
@@ -282,7 +282,7 @@ public function test_current_user_can_set_authors_using_coauthors_plus_edit_auth
 	/**
 	 * Checks if the current user can edit a post they are set as a coauthor for.
 	 */
-	public function test_current_user_can_edit_post_they_coauthor() {
+	public function test_current_user_can_edit_post_they_coauthor(): void {
 		global $coauthors_plus;
 
 		// Backing up current user.
@@ -328,7 +328,7 @@ public function test_current_user_can_edit_post_they_coauthor() {
 	 *
 	 * @covers CoAuthors_Plus::search_authors()
 	 */
-	public function test_search_authors_no_args() {
+	public function test_search_authors_no_args(): void {
 
 		global $coauthors_plus;
 
@@ -372,7 +372,7 @@ public function test_search_authors_no_args() {
 	 *
 	 * @covers CoAuthors_Plus::search_authors()
 	 */
-	public function test_search_authors_when_search_keyword_provided() {
+	public function test_search_authors_when_search_keyword_provided(): void {
 
 		global $coauthors_plus;
 
@@ -426,7 +426,7 @@ public function test_search_authors_when_search_keyword_provided() {
 	 *
 	 * @covers CoAuthors_Plus::search_authors()
 	 */
-	public function test_search_authors_when_ignored_authors_provided() {
+	public function test_search_authors_when_ignored_authors_provided(): void {
 
 		global $coauthors_plus;
 
@@ -465,7 +465,7 @@ public function test_search_authors_when_ignored_authors_provided() {
 	 *
 	 * @covers CoAuthors_Plus::search_authors()
 	 */
-	public function test_search_authors_when_search_keyword_and_ignored_authors_provided() {
+	public function test_search_authors_when_search_keyword_and_ignored_authors_provided(): void {
 
 		global $coauthors_plus;
 
@@ -494,7 +494,7 @@ public function test_search_authors_when_search_keyword_and_ignored_authors_prov
 	 *
 	 * @covers CoAuthors_Plus::get_author_term()
 	 */
-	public function test_get_author_term_when_coauthor_is_not_object() {
+	public function test_get_author_term_when_coauthor_is_not_object(): void {
 
 		global $coauthors_plus;
 
@@ -508,7 +508,7 @@ public function test_get_author_term_when_coauthor_is_not_object() {
 	 *
 	 * @covers CoAuthors_Plus::get_author_term()
 	 */
-	public function test_get_author_term_using_caching() {
+	public function test_get_author_term_using_caching(): void {
 
 		global $coauthors_plus;
 
@@ -530,7 +530,7 @@ public function test_get_author_term_using_caching() {
 	 *
 	 * @covers CoAuthors_Plus::get_author_term()
 	 */
-	public function test_get_author_term_when_author_has_linked_account() {
+	public function test_get_author_term_when_author_has_linked_account(): void {
 
 		global $coauthors_plus;
 
@@ -553,7 +553,7 @@ public function test_get_author_term_when_author_has_linked_account() {
 	 *
 	 * @covers CoAuthors_Plus::get_author_term()
 	 */
-	public function test_get_author_term_when_author_has_not_linked_account() {
+	public function test_get_author_term_when_author_has_not_linked_account(): void {
 
 		global $coauthors_plus;
 
@@ -581,7 +581,7 @@ public function test_get_author_term_when_author_has_not_linked_account() {
 	 *
 	 * @covers CoAuthors_Plus::update_author_term()
 	 */
-	public function test_update_author_term_when_coauthor_is_not_object() {
+	public function test_update_author_term_when_coauthor_is_not_object(): void {
 
 		global $coauthors_plus;
 
@@ -595,7 +595,7 @@ public function test_update_author_term_when_coauthor_is_not_object() {
 	 *
 	 * @covers CoAuthors_Plus::update_author_term()
 	 */
-	public function test_update_author_term_when_author_term_exists() {
+	public function test_update_author_term_when_author_term_exists(): void {
 
 		global $coauthors_plus;
 
@@ -641,7 +641,7 @@ public function test_update_author_term_when_author_term_exists() {
 	 *
 	 * @covers CoAuthors_Plus::update_author_term()
 	 */
-	public function test_update_author_term_when_author_term_not_exist() {
+	public function test_update_author_term_when_author_term_not_exist(): void {
 
 		global $coauthors_plus;
 
@@ -684,7 +684,7 @@ public function test_update_author_term_when_author_term_not_exist() {
 	/**
 	 * @covers CoAuthors_Plus::is_block_editor()
 	 */
-	public function test_is_block_editor() {
+	public function test_is_block_editor(): void {
 		global $coauthors_plus;
 
 		set_current_screen( 'post-new.php' );
@@ -699,7 +699,7 @@ public function test_is_block_editor() {
 	/**
 	 * @covers CoAuthors_Plus::enqueue_sidebar_plugin_assets()
 	 */
-	public function test_enqueue_editor_assets() {
+	public function test_enqueue_editor_assets(): void {
 
 		// Default state
 		do_action( 'enqueue_block_editor_assets' );
@@ -721,7 +721,7 @@ public function test_enqueue_editor_assets() {
 	/**
 	 * @covers CoAuthors_Plus::add_coauthors_box()
 	 */
-	public function test_add_coauthors_box() {
+	public function test_add_coauthors_box(): void {
 		global $coauthors_plus, $wp_meta_boxes;
 
 		wp_set_current_user( $this->editor1->ID );
@@ -736,7 +736,7 @@ public function test_add_coauthors_box() {
 	/**
 	 * Test the expected default supported post types.
 	 */
-	public function test_default_supported_post_types() {
+	public function test_default_supported_post_types(): void {
 		$supported_post_types = (new \CoAuthors_Plus())->supported_post_types();
 		$expected = array(
 			'post',
@@ -748,7 +748,7 @@ public function test_default_supported_post_types() {
 	/**
 	 * Test whether the supported post types can be filtered.
 	 */
-	public function test_can_filter_supported_post_types() {
+	public function test_can_filter_supported_post_types(): void {
 		// This should be detected.
 		$post_type_with_author = register_post_type(
 			'foo',
diff --git a/tests/Integration/EndpointsTest.php b/tests/Integration/EndpointsTest.php
index 55004353..519d0e15 100644
--- a/tests/Integration/EndpointsTest.php
+++ b/tests/Integration/EndpointsTest.php
@@ -29,7 +29,7 @@ public function set_up() {
 	/**
 	 * @covers \CoAuthors\API\Endpoints::__construct
 	 */
-	public function test_construct() {
+	public function test_construct(): void {
 
 		$this->assertEquals(
 			10,
@@ -58,7 +58,7 @@ public function test_construct() {
 	/**
 	 * @covers \CoAuthors\API\Endpoints::add_endpoints
 	 */
-	public function test_add_endpoints() {
+	public function test_add_endpoints(): void {
 
 		$rest_server = rest_get_server();
 
@@ -117,7 +117,7 @@ public function test_add_endpoints() {
 	/**
 	 * @covers \CoAuthors\API\Endpoints::get_coauthors_search_results
 	 */
-	public function test_get_coauthors_search_results() {
+	public function test_get_coauthors_search_results(): void {
 		$author1 = $this->create_author( 'author1' );
 		$author2 = $this->create_author( 'author2' );
 		$guest_author1 = $this->create_guest_author( 'guest_author1' );
@@ -165,7 +165,7 @@ public function test_get_coauthors_search_results() {
 	/**
 	 * @covers \CoAuthors\API\Endpoints::get_coauthors
 	 */
-	public function test_authors_get_coauthors() {
+	public function test_authors_get_coauthors(): void {
 		$author = $this->create_author();
 		$post   = $this->create_post( $author );
 
@@ -183,7 +183,7 @@ public function test_authors_get_coauthors() {
 	/**
 	 * @covers \CoAuthors\API\Endpoints::update_coauthors
 	 */
-	public function test_update_coauthors() {
+	public function test_update_coauthors(): void {
 		$author       = $this->create_author();
 		$editor       = $this->create_editor();
 		$guest_author = $this->create_guest_author();
@@ -203,7 +203,7 @@ public function test_update_coauthors() {
 		$this->assertCount( 2, $update_response->data );
 	}
 
-	public function data_only_editor_role_can_edit_coauthors() {
+	public function data_only_editor_role_can_edit_coauthors(): array {
 		return array(
 			'Subscriber' => array(
 				'subscriber',
@@ -231,7 +231,7 @@ public function data_only_editor_role_can_edit_coauthors() {
 	 *
 	 * @return void
 	 */
-	public function test_which_role_can_edit_coauthors( $role_name, $outcome ) {
+	public function test_which_role_can_edit_coauthors( $role_name, $outcome ): void {
 		$role = $this->{"create_$role_name"}();
 		wp_set_current_user( $role->ID );
 		$this->assertEquals( $outcome, $this->_api->can_edit_coauthors() );
@@ -240,7 +240,7 @@ public function test_which_role_can_edit_coauthors( $role_name, $outcome ) {
 	/**
 	 * @covers \CoAuthors\API\Endpoints::remove_author_link
 	 */
-	public function test_remove_author_link() {
+	public function test_remove_author_link(): void {
 		$editor = $this->create_editor();
 		$post   = $this->create_post( $editor );
 
@@ -276,7 +276,7 @@ public function test_remove_author_link() {
 	/**
 	 * @covers \CoAuthors\API\Endpoints::modify_responses
 	 */
-	public function test_modify_response() {
+	public function test_modify_response(): void {
 		$this->_api->modify_responses();
 
 		foreach ( $this->_cap->supported_post_types() as $post_type ) {
diff --git a/tests/Integration/GuestAuthorsTest.php b/tests/Integration/GuestAuthorsTest.php
index 84f2b218..9febe0dc 100644
--- a/tests/Integration/GuestAuthorsTest.php
+++ b/tests/Integration/GuestAuthorsTest.php
@@ -50,7 +50,7 @@ public function set_up() {
 	 *
 	 * @covers CoAuthors_Guest_Authors::get_guest_author_by()
 	 */
-	public function test_get_guest_author_by_with_empty_key_or_value() {
+	public function test_get_guest_author_by_with_empty_key_or_value(): void {
 
 		global $coauthors_plus;
 
@@ -72,7 +72,7 @@ public function test_get_guest_author_by_with_empty_key_or_value() {
 	 *
 	 * @covers CoAuthors_Guest_Authors::get_guest_author_by()
 	 */
-	public function test_get_guest_author_by_using_cache() {
+	public function test_get_guest_author_by_using_cache(): void {
 
 		global $coauthors_plus;
 
@@ -98,7 +98,7 @@ public function test_get_guest_author_by_using_cache() {
 	 *
 	 * @covers CoAuthors_Guest_Authors::get_guest_author_by()
 	 */
-	public function test_get_guest_author_by_with_different_keys() {
+	public function test_get_guest_author_by_with_different_keys(): void {
 
 		global $coauthors_plus;
 
@@ -135,7 +135,7 @@ public function test_get_guest_author_by_with_different_keys() {
 	 *
 	 * @covers CoAuthors_Guest_Authors::get_guest_author_thumbnail()
 	 */
-	public function test_get_guest_author_thumbnail() {
+	public function test_get_guest_author_thumbnail(): void {
 
 		global $coauthors_plus;
 
@@ -170,7 +170,7 @@ public function test_get_guest_author_thumbnail() {
 	 *
 	 * @covers CoAuthors_Guest_Authors::get_guest_author_fields()
 	 */
-	public function test_get_guest_author_fields() {
+	public function test_get_guest_author_fields(): void {
 
 		global $coauthors_plus;
 
@@ -232,7 +232,7 @@ public function test_get_guest_author_fields() {
 	 *
 	 * @covers CoAuthors_Guest_Authors::get_all_linked_accounts()
 	 */
-	public function test_get_all_linked_accounts() {
+	public function test_get_all_linked_accounts(): void {
 
 		global $coauthors_plus;
 
@@ -266,7 +266,7 @@ public function test_get_all_linked_accounts() {
 	 *
 	 * @covers CoAuthors_Guest_Authors::get_all_linked_accounts()
 	 */
-	public function test_get_all_linked_accounts_with_cache() {
+	public function test_get_all_linked_accounts_with_cache(): void {
 
 		global $coauthors_plus;
 
@@ -291,7 +291,7 @@ public function test_get_all_linked_accounts_with_cache() {
 	 *
 	 * @covers CoAuthors_Guest_Authors::create_guest_author_from_user_id()
 	 */
-	public function test_create_guest_author_from_user_id() {
+	public function test_create_guest_author_from_user_id(): void {
 
 		global $coauthors_plus;
 
@@ -315,7 +315,7 @@ public function test_create_guest_author_from_user_id() {
 	 *
 	 * @covers CoAuthors_Guest_Authors::handle_delete_guest_author_action()
 	 */
-	public function test_handle_delete_guest_author_action_when_post_args_not_as_expected() {
+	public function test_handle_delete_guest_author_action_when_post_args_not_as_expected(): void {
 
 		global $coauthors_plus;
 
@@ -370,7 +370,7 @@ public function test_handle_delete_guest_author_action_when_post_args_not_as_exp
 	 *
 	 * @covers CoAuthors_Guest_Authors::handle_delete_guest_author_action()
 	 */
-	public function test_handle_delete_guest_author_action_with_nonce() {
+	public function test_handle_delete_guest_author_action_with_nonce(): void {
 
 		global $coauthors_plus;
 
@@ -417,7 +417,7 @@ public function test_handle_delete_guest_author_action_with_nonce() {
 	 *
 	 * @covers CoAuthors_Guest_Authors::handle_delete_guest_author_action()
 	 */
-	public function test_handle_delete_guest_author_action_with_list_users_capability() {
+	public function test_handle_delete_guest_author_action_with_list_users_capability(): void {
 
 		global $coauthors_plus;
 
@@ -475,7 +475,7 @@ public function test_handle_delete_guest_author_action_with_list_users_capabilit
 	 *
 	 * @covers CoAuthors_Guest_Authors::handle_delete_guest_author_action()
 	 */
-	public function test_handle_delete_guest_author_action_with_guest_author_existence() {
+	public function test_handle_delete_guest_author_action_with_guest_author_existence(): void {
 
 		global $coauthors_plus;
 
@@ -529,7 +529,7 @@ public function test_handle_delete_guest_author_action_with_guest_author_existen
 	 *
 	 * @covers CoAuthors_Guest_Authors::handle_delete_guest_author_action()
 	 */
-	public function test_handle_delete_guest_author_action_with_reassign_not_as_expected() {
+	public function test_handle_delete_guest_author_action_with_reassign_not_as_expected(): void {
 
 		global $coauthors_plus;
 
@@ -573,7 +573,7 @@ public function test_handle_delete_guest_author_action_with_reassign_not_as_expe
 	 *
 	 * @covers CoAuthors_Guest_Authors::handle_delete_guest_author_action()
 	 */
-	public function test_handle_delete_guest_author_action_with_reassign_is_leave_assigned() {
+	public function test_handle_delete_guest_author_action_with_reassign_is_leave_assigned(): void {
 
 		global $coauthors_plus;
 
@@ -619,7 +619,7 @@ public function test_handle_delete_guest_author_action_with_reassign_is_leave_as
 	 *
 	 * @covers CoAuthors_Guest_Authors::handle_delete_guest_author_action()
 	 */
-	public function test_handle_delete_guest_author_action_with_reassign_is_reassign_another() {
+	public function test_handle_delete_guest_author_action_with_reassign_is_reassign_another(): void {
 
 		global $coauthors_plus;
 
@@ -682,7 +682,7 @@ public function test_handle_delete_guest_author_action_with_reassign_is_reassign
 	 *
 	 * @covers CoAuthors_Guest_Authors::handle_delete_guest_author_action()
 	 */
-	public function test_handle_delete_guest_author_action_with_reassign_is_remove_byline() {
+	public function test_handle_delete_guest_author_action_with_reassign_is_remove_byline(): void {
 
 		global $coauthors_plus;
 
@@ -736,7 +736,7 @@ public function test_handle_delete_guest_author_action_with_reassign_is_remove_b
 	 *
 	 * @return void
 	 **/
-	public function catch_redirect_destination( $location, $status ) {
+	public function catch_redirect_destination( $location, $status ): void {
 
 		throw new \Exception( $location, $status );
 	}
@@ -746,7 +746,7 @@ public function catch_redirect_destination( $location, $status ) {
 	 *
 	 * @covers CoAuthors_Guest_Authors::delete()
 	 */
-	public function test_delete_when_guest_author_not_exist() {
+	public function test_delete_when_guest_author_not_exist(): void {
 
 		global $coauthors_plus;
 
@@ -763,7 +763,7 @@ public function test_delete_when_guest_author_not_exist() {
 	 *
 	 * @covers CoAuthors_Guest_Authors::delete()
 	 */
-	public function test_delete_without_reassign() {
+	public function test_delete_without_reassign(): void {
 
 		global $coauthors_plus;
 
@@ -786,7 +786,7 @@ public function test_delete_without_reassign() {
 	 *
 	 * @covers CoAuthors_Guest_Authors::delete()
 	 */
-	public function test_delete_with_reassign_author_not_exist() {
+	public function test_delete_with_reassign_author_not_exist(): void {
 
 		global $coauthors_plus;
 
@@ -807,7 +807,7 @@ public function test_delete_with_reassign_author_not_exist() {
 	 *
 	 * @covers CoAuthors_Guest_Authors::delete()
 	 */
-	public function test_delete_with_reassign_when_linked_account_and_author_are_same_user() {
+	public function test_delete_with_reassign_when_linked_account_and_author_are_same_user(): void {
 
 		global $coauthors_plus;
 
@@ -830,7 +830,7 @@ public function test_delete_with_reassign_when_linked_account_and_author_are_sam
 	 *
 	 * @covers CoAuthors_Guest_Authors::delete()
 	 */
-	public function test_delete_with_reassign_when_linked_account_and_author_are_different_user() {
+	public function test_delete_with_reassign_when_linked_account_and_author_are_different_user(): void {
 
 		global $coauthors_plus;
 
@@ -864,7 +864,7 @@ public function test_delete_with_reassign_when_linked_account_and_author_are_dif
 	 *
 	 * @covers CoAuthors_Guest_Authors::delete()
 	 */
-	public function test_delete_with_reassign_without_linked_account_and_author_is_same_user() {
+	public function test_delete_with_reassign_without_linked_account_and_author_is_same_user(): void {
 
 		global $coauthors_plus;
 
@@ -891,7 +891,7 @@ public function test_delete_with_reassign_without_linked_account_and_author_is_s
 	 *
 	 * @covers CoAuthors_Guest_Authors::delete()
 	 */
-	public function test_delete_with_reassign_without_linked_account_and_author_is_other_user() {
+	public function test_delete_with_reassign_without_linked_account_and_author_is_other_user(): void {
 
 		global $coauthors_plus;
 
diff --git a/tests/Integration/ManageCoAuthorsTest.php b/tests/Integration/ManageCoAuthorsTest.php
index 5c340814..86ed4197 100644
--- a/tests/Integration/ManageCoAuthorsTest.php
+++ b/tests/Integration/ManageCoAuthorsTest.php
@@ -87,14 +87,14 @@ public function set_up() {
 		$this->author1_page2 = wp_insert_post( $page );
 	}
 
-	public function tear_down() {
+	public function tear_down(): void {
 		parent::tear_down();
 	}
 
 	/**
 	 * Test assigning a Co-Author to a post
 	 */
-	public function test_add_coauthor_to_post() {
+	public function test_add_coauthor_to_post(): void {
 		global $coauthors_plus;
 
 		$coauthors = get_coauthors( $this->author1_post1 );
@@ -119,7 +119,7 @@ public function test_add_coauthor_to_post() {
 	 *
 	 * @see https://github.com/Automattic/Co-Authors-Plus/issues/140
 	 */
-	public function test_add_coauthor_updates_post_author() {
+	public function test_add_coauthor_updates_post_author(): void {
 		global $coauthors_plus;
 
 		// append = true, preserves existing post_author
@@ -138,7 +138,7 @@ public function test_add_coauthor_updates_post_author() {
 	 *
 	 * @see https://github.com/Automattic/Co-Authors-Plus/issues/170
 	 */
-	public function test_post_publish_count_for_coauthor() {
+	public function test_post_publish_count_for_coauthor(): void {
 		global $coauthors_plus;
 
 		$editor1 = get_user_by( 'id', $this->editor1 );
@@ -191,7 +191,7 @@ public function test_post_publish_count_for_coauthor() {
 	 *
 	 * @covers \CoAuthors_Plus::coauthors_set_post_author_field
 	 */
-	public function test_coauthors_set_post_author_field_when_post_type_is_attachment() {
+	public function test_coauthors_set_post_author_field_when_post_type_is_attachment(): void {
 
 		global $coauthors_plus;
 
@@ -233,7 +233,7 @@ public function test_coauthors_set_post_author_field_when_post_type_is_attachmen
 	 *
 	 * @covers \CoAuthors_Plus::coauthors_set_post_author_field
 	 */
-	public function test_coauthors_set_post_author_field_when_coauthor_is_not_set() {
+	public function test_coauthors_set_post_author_field_when_coauthor_is_not_set(): void {
 
 		global $coauthors_plus;
 
@@ -257,7 +257,7 @@ public function test_coauthors_set_post_author_field_when_coauthor_is_not_set()
 	 *
 	 * @covers \CoAuthors_Plus::coauthors_set_post_author_field
 	 */
-	public function test_coauthors_set_post_author_field_when_coauthor_is_set() {
+	public function test_coauthors_set_post_author_field_when_coauthor_is_set(): void {
 
 		global $coauthors_plus;
 
@@ -310,7 +310,7 @@ public function test_coauthors_set_post_author_field_when_coauthor_is_set() {
 	 *
 	 * @covers \CoAuthors_Plus::coauthors_set_post_author_field
 	 */
-	public function test_coauthors_set_post_author_field_when_guest_author_is_linked_with_wp_user() {
+	public function test_coauthors_set_post_author_field_when_guest_author_is_linked_with_wp_user(): void {
 
 		global $coauthors_plus;
 
@@ -354,7 +354,7 @@ public function test_coauthors_set_post_author_field_when_guest_author_is_linked
 	 *
 	 * @covers \CoAuthors_Plus::coauthors_set_post_author_field
 	 */
-	public function test_coauthors_set_post_author_field_when_post_author_is_not_set() {
+	public function test_coauthors_set_post_author_field_when_post_author_is_not_set(): void {
 
 		global $coauthors_plus;
 
@@ -392,7 +392,7 @@ public function test_coauthors_set_post_author_field_when_post_author_is_not_set
 	 *
 	 * @covers \CoAuthors_Plus::coauthors_update_post
 	 */
-	public function test_coauthors_update_post_when_post_type_is_attachment() {
+	public function test_coauthors_update_post_when_post_type_is_attachment(): void {
 
 		global $coauthors_plus;
 
@@ -427,7 +427,7 @@ public function test_coauthors_update_post_when_post_type_is_attachment() {
 	 *
 	 * @covers \CoAuthors_Plus::coauthors_update_post
 	 */
-	public function test_coauthors_update_post_when_current_user_can_set_authors() {
+	public function test_coauthors_update_post_when_current_user_can_set_authors(): void {
 
 		global $coauthors_plus;
 
@@ -473,7 +473,7 @@ public function test_coauthors_update_post_when_current_user_can_set_authors() {
 	 *
 	 * @covers \CoAuthors_Plus::coauthors_update_post
 	 */
-	public function test_coauthors_update_post_when_post_has_not_author_terms() {
+	public function test_coauthors_update_post_when_post_has_not_author_terms(): void {
 
 		global $coauthors_plus;
 
diff --git a/tests/Integration/TemplateTags/CoauthorsGetAvatarTest.php b/tests/Integration/TemplateTags/CoauthorsGetAvatarTest.php
index 95c823bc..d1eef2cb 100644
--- a/tests/Integration/TemplateTags/CoauthorsGetAvatarTest.php
+++ b/tests/Integration/TemplateTags/CoauthorsGetAvatarTest.php
@@ -12,7 +12,7 @@ class CoauthorsGetAvatarTest extends TestCase {
 	/**
 	 * Checks co-author's avatar.
 	 */
-	public function test_with_author() {
+	public function test_with_author(): void {
 		$author = $this->create_author();
 
 		$this->assertEmpty( coauthors_get_avatar( $author->ID ) );
@@ -22,7 +22,7 @@ public function test_with_author() {
 	/**
 	 * Checks co-author's avatar when author is a guest author.
 	 */
-	public function test_with_guest_author() {
+	public function test_with_guest_author(): void {
 		global $coauthors_plus;
 
 		$guest_author_id = $this->create_guest_author();
@@ -45,7 +45,7 @@ public function test_with_guest_author() {
 	/**
 	 * Checks co-author's avatar when user's email is not set somehow.
 	 */
-	public function test_with_guest_author_when_user_email_not_set() {
+	public function test_with_guest_author_when_user_email_not_set(): void {
 		global $coauthors_plus;
 
 		$guest_author_id = $this->create_guest_author();
@@ -58,7 +58,7 @@ public function test_with_guest_author_when_user_email_not_set() {
 	/**
 	 * Checks co-author's avatar with size.
 	 */
-	public function test_with_author_and_size_arg() {
+	public function test_with_author_and_size_arg(): void {
 		$author = $this->create_author();
 		$size = '100';
 
@@ -68,7 +68,7 @@ public function test_with_author_and_size_arg() {
 	/**
 	 * Checks co-author's avatar with alt.
 	 */
-	public function test_with_author_and_alt_arg() {
+	public function test_with_author_and_alt_arg(): void {
 		$author = $this->create_author();
 		$alt = 'Test';
 
diff --git a/tests/Integration/TemplateTags/CoauthorsPostsLinksSingleTest.php b/tests/Integration/TemplateTags/CoauthorsPostsLinksSingleTest.php
index 83ba4c18..d8e0401f 100644
--- a/tests/Integration/TemplateTags/CoauthorsPostsLinksSingleTest.php
+++ b/tests/Integration/TemplateTags/CoauthorsPostsLinksSingleTest.php
@@ -15,7 +15,7 @@ class CoauthorsPostsLinksSingleTest extends TestCase {
 	/**
 	 * Checks _doing_it_wrong() is called if author object is incomplete.
 	 */
-	public function test_null_is_returned_if_author_object_is_incomplete() {
+	public function test_null_is_returned_if_author_object_is_incomplete(): void {
 		$author = $this->create_author();
 		$this->setExpectedIncorrectUsage( 'coauthors_posts_links_single' );
 		unset( $author->ID, $author->user_nicename, $author->display_name );
@@ -26,7 +26,7 @@ public function test_null_is_returned_if_author_object_is_incomplete() {
 	/**
 	 * Checks single co-author linked to their post archive.
 	 */
-	public function test_single_link_is_returned_with_default_args() {
+	public function test_single_link_is_returned_with_default_args(): void {
 		$author = $this->create_author();
 
 		$author_link = coauthors_posts_links_single( $author );
@@ -41,7 +41,7 @@ public function test_single_link_is_returned_with_default_args() {
 	/**
 	 * Checks single co-author linked to their post archive.
 	 */
-	public function test_single_link_is_returned_with_filtered_args() {
+	public function test_single_link_is_returned_with_filtered_args(): void {
 		$author = $this->create_author( 'filtered-author' );
 		add_filter( 'coauthors_posts_link', function( $args ) use ( $author ) {
 			return array(
diff --git a/tests/Integration/TemplateTags/CoauthorsPostsLinksTest.php b/tests/Integration/TemplateTags/CoauthorsPostsLinksTest.php
index 4c15623a..9ed7114d 100644
--- a/tests/Integration/TemplateTags/CoauthorsPostsLinksTest.php
+++ b/tests/Integration/TemplateTags/CoauthorsPostsLinksTest.php
@@ -12,7 +12,7 @@ class CoauthorsPostsLinksTest extends TestCase {
 	/**
 	 * Test the author filter is retained.
 	 */
-	public function test_the_author_filter_is_retained() {
+	public function test_the_author_filter_is_retained(): void {
 		global $coauthors_plus_template_filters;
 		$coauthors_plus_template_filters = new \CoAuthors_Template_Filters();
 		$this->assertEquals( 10, has_filter( 'the_author', array( $coauthors_plus_template_filters, 'filter_the_author' ) ) );
@@ -24,7 +24,7 @@ public function test_the_author_filter_is_retained() {
 	 *
 	 * @see https://github.com/Automattic/Co-Authors-Plus/issues/279
 	 */
-	public function test_coauthors_posts_links_for_single_author() {
+	public function test_coauthors_posts_links_for_single_author(): void {
 		$author = $this->create_author();
 		$post   = $this->create_post( $author );
 		$GLOBALS['post'] = $post;
@@ -41,7 +41,7 @@ public function test_coauthors_posts_links_for_single_author() {
 	/**
 	 * Test co-author posts links are retrieved for multiple authors and default args.
 	 */
-	public function test_coauthors_posts_links_for_multiple_authors_with_default_args() {
+	public function test_coauthors_posts_links_for_multiple_authors_with_default_args(): void {
 		global $coauthors_plus;
 
 		$author = $this->create_author();
@@ -62,7 +62,7 @@ public function test_coauthors_posts_links_for_multiple_authors_with_default_arg
 	/**
 	 * Test that co-author posts link is retrieved via coauthors_posts_links_single() but for multiple authors.
 	 */
-	public function test_coauthors_posts_links_for_multiple_authors_with_amended_args() {
+	public function test_coauthors_posts_links_for_multiple_authors_with_amended_args(): void {
 		global $coauthors_plus;
 
 		$author1 = $this->create_author( 'author1' );
diff --git a/tests/Integration/TemplateTags/CoauthorsWpListAuthorsTest.php b/tests/Integration/TemplateTags/CoauthorsWpListAuthorsTest.php
index 88feaf34..ce51c222 100644
--- a/tests/Integration/TemplateTags/CoauthorsWpListAuthorsTest.php
+++ b/tests/Integration/TemplateTags/CoauthorsWpListAuthorsTest.php
@@ -12,7 +12,7 @@ class CoauthorsWpListAuthorsTest extends TestCase {
 	/**
 	 * Checks all the co-authors of the blog with default args.
 	 */
-	public function test_list_authors_with_default_args() {
+	public function test_list_authors_with_default_args(): void {
 
 		global $coauthors_plus;
 
@@ -57,7 +57,7 @@ public function test_list_authors_with_default_args() {
 	/**
 	 * Checks all the co-authors of the blog with optioncount option.
 	 */
-	public function test_list_authors_with_optioncount_arg_enabled() {
+	public function test_list_authors_with_optioncount_arg_enabled(): void {
 		$author = $this->create_author();
 		$post   = $this->create_post( $author );
 
@@ -75,7 +75,7 @@ public function test_list_authors_with_optioncount_arg_enabled() {
 	/**
 	 * Checks all the co-authors of the blog with show_fullname option.
 	 */
-	public function test_list_authors_with_show_fullname_arg_enabled() {
+	public function test_list_authors_with_show_fullname_arg_enabled(): void {
 		$author = $this->create_author();
 		$post   = $this->create_post( $author );
 
@@ -105,7 +105,7 @@ public function test_list_authors_with_show_fullname_arg_enabled() {
 	/**
 	 * Checks all the co-authors of the blog with hide_empty option.
 	 */
-	public function test_list_authors_with_hide_empty_arg_enabled() {
+	public function test_list_authors_with_hide_empty_arg_enabled(): void {
 
 		global $coauthors_plus;
 
@@ -130,7 +130,7 @@ public function test_list_authors_with_hide_empty_arg_enabled() {
 	/**
 	 * Checks all the co-authors of the blog with feed option.
 	 */
-	public function test_list_authors_with_feed_arg_enabled() {
+	public function test_list_authors_with_feed_arg_enabled(): void {
 		$author = $this->create_author();
 		$post   = $this->create_post( $author );
 
@@ -149,7 +149,7 @@ public function test_list_authors_with_feed_arg_enabled() {
 	/**
 	 * Checks all the co-authors of the blog with feed_image option.
 	 */
-	public function test_list_authors_with_feed_image_arg_enabled() {
+	public function test_list_authors_with_feed_image_arg_enabled(): void {
 		$author = $this->create_author();
 		$post   = $this->create_post( $author );
 
@@ -168,7 +168,7 @@ public function test_list_authors_with_feed_image_arg_enabled() {
 	/**
 	 * Checks all the co-authors of the blog with feed_type option.
 	 */
-	public function test_list_authors_with_feed_type_arg_enabled() {
+	public function test_list_authors_with_feed_type_arg_enabled(): void {
 		$author = $this->create_author();
 		$post   = $this->create_post( $author );
 
@@ -190,7 +190,7 @@ public function test_list_authors_with_feed_type_arg_enabled() {
 	/**
 	 * Checks all the co-authors of the blog with style option.
 	 */
-	public function test_list_authors_with_style_arg_enabled() {
+	public function test_list_authors_with_style_arg_enabled(): void {
 
 		$coauthors = coauthors_wp_list_authors(
 			array(
@@ -206,7 +206,7 @@ public function test_list_authors_with_style_arg_enabled() {
 	/**
 	 * Checks all the co-authors of the blog with html option.
 	 */
-	public function test_list_authors_with_html_arg_enabled() {
+	public function test_list_authors_with_html_arg_enabled(): void {
 		global $coauthors_plus;
 
 		$author = $this->create_author();
@@ -228,7 +228,7 @@ public function test_list_authors_with_html_arg_enabled() {
 	/**
 	 * Checks all the co-authors of the blog with guest_authors_only option.
 	 */
-	public function test_list_authors_with_guest_authors_only_arg_enabled() {
+	public function test_list_authors_with_guest_authors_only_arg_enabled(): void {
 
 		global $coauthors_plus;
 
diff --git a/tests/Integration/TemplateTags/GetCoauthorsTest.php b/tests/Integration/TemplateTags/GetCoauthorsTest.php
index f59b2f57..ea4c5790 100644
--- a/tests/Integration/TemplateTags/GetCoauthorsTest.php
+++ b/tests/Integration/TemplateTags/GetCoauthorsTest.php
@@ -12,14 +12,14 @@ class GetCoauthorsTest extends TestCase {
 	/**
 	 * Checks coauthors when post not exist.
 	 */
-	public function test_get_coauthors_when_post_not_exists() {
+	public function test_get_coauthors_when_post_not_exists(): void {
 		$this->assertEmpty( get_coauthors() );
 	}
 
 	/**
 	 * Checks coauthors when post exist (not global).
 	 */
-	public function test_get_coauthors_when_post_exists() {
+	public function test_get_coauthors_when_post_exists(): void {
 		$author = $this->create_author();
 		$editor = $this->create_editor();
 		$post   = $this->create_post( $author );
@@ -43,7 +43,7 @@ public function test_get_coauthors_when_post_exists() {
 	/**
 	 * Checks coauthors when terms for post not exist.
 	 */
-	public function test_get_coauthors_when_terms_for_post_not_exists() {
+	public function test_get_coauthors_when_terms_for_post_not_exists(): void {
 
 		$post_id = $this->factory()->post->create();
 		$this->assertEmpty( get_coauthors( $post_id ) );
@@ -52,7 +52,7 @@ public function test_get_coauthors_when_terms_for_post_not_exists() {
 	/**
 	 * Checks coauthors when post not exist but global post does.
 	 */
-	public function test_get_coauthors_when_global_post_exists() {
+	public function test_get_coauthors_when_global_post_exists(): void {
 
 		global $post;
 
@@ -80,7 +80,7 @@ public function test_get_coauthors_when_global_post_exists() {
 	/**
 	 * Checks coauthors when post not exist but global post_ID does.
 	 */
-	public function test_get_coauthors_when_global_post_id_exists() {
+	public function test_get_coauthors_when_global_post_id_exists(): void {
 
 		global $post_ID;
 
@@ -111,7 +111,7 @@ public function test_get_coauthors_when_global_post_id_exists() {
 	/**
 	 * Checks coauthors order.
 	 */
-	public function test_coauthors_order() {
+	public function test_coauthors_order(): void {
 
 		global $coauthors_plus;
 
diff --git a/tests/Integration/TemplateTags/IsCoauthorForPostTest.php b/tests/Integration/TemplateTags/IsCoauthorForPostTest.php
index 4a66bc87..6a61ee8e 100644
--- a/tests/Integration/TemplateTags/IsCoauthorForPostTest.php
+++ b/tests/Integration/TemplateTags/IsCoauthorForPostTest.php
@@ -12,7 +12,7 @@ class IsCoauthorForPostTest extends TestCase {
 	/**
 	 * Checks whether a non-existent user is a coauthor of a post.
 	 */
-	public function test_return_false_when_user_is_not_valid() {
+	public function test_return_false_when_user_is_not_valid(): void {
 		$author = $this->create_author();
 		$post   = $this->create_post( $author );
 		$user = new \WP_User();
@@ -25,7 +25,7 @@ public function test_return_false_when_user_is_not_valid() {
 	/**
 	 * Checks whether a user is a coauthor of a non-existent post.
 	 */
-	public function test_return_false_when_post_does_not_exist() {
+	public function test_return_false_when_post_does_not_exist(): void {
 		$author = $this->create_author();
 		$post   = $this->create_post( $author );
 
@@ -35,7 +35,7 @@ public function test_return_false_when_post_does_not_exist() {
 	/**
 	 * Checks whether a user is a coauthor of a non-existent post.
 	 */
-	public function test_return_false_when_post_is_not_provided_and_global_post_is_not_set() {
+	public function test_return_false_when_post_is_not_provided_and_global_post_is_not_set(): void {
 		$author = $this->create_author();
 		unset( $GLOBALS['post'] );
 
@@ -46,7 +46,7 @@ public function test_return_false_when_post_is_not_provided_and_global_post_is_n
 	 * Checks whether user is a coauthor of the post when user is set in either way,
 	 * as user_id or user object but he/she is not coauthor of the post.
 	 */
-	public function test_is_coauthor_for_post_when_user_numeric_or_user_login_set_but_not_coauthor() {
+	public function test_is_coauthor_for_post_when_user_numeric_or_user_login_set_but_not_coauthor(): void {
 		$author = $this->create_author();
 		$editor = $this->create_editor();
 		$post   = $this->create_post( $author );
@@ -58,7 +58,7 @@ public function test_is_coauthor_for_post_when_user_numeric_or_user_login_set_bu
 	/**
 	 * Checks whether user is a coauthor of the post.
 	 */
-	public function test_is_coauthor_for_post_when_user_is_coauthor() {
+	public function test_is_coauthor_for_post_when_user_is_coauthor(): void {
 		$author = $this->create_author();
 		$editor = $this->create_editor();
 		$post   = $this->create_post( $author );
diff --git a/tests/Integration/TemplateTagsTest.php b/tests/Integration/TemplateTagsTest.php
index ab12bb1d..d96ecbb9 100644
--- a/tests/Integration/TemplateTagsTest.php
+++ b/tests/Integration/TemplateTagsTest.php
@@ -52,7 +52,7 @@ public function set_up() {
 	 *
 	 * @covers ::coauthors_links()
 	 */
-	public function test_coauthors_links() {
+	public function test_coauthors_links(): void {
 
 		global $coauthors_plus, $coauthors_plus_template_filters;
 
@@ -102,7 +102,7 @@ public function test_coauthors_links() {
 	 * @covers ::coauthors()
 	 * @covers ::coauthors__echo()
 	 **/
-	public function test_coauthors() {
+	public function test_coauthors(): void {
 
 		global $post, $coauthors_plus;
 
@@ -141,7 +141,7 @@ public function test_coauthors() {
 	 * @covers ::coauthors_firstnames()
 	 * @covers ::coauthors__echo()
 	 */
-	public function test_coauthors_firstnames() {
+	public function test_coauthors_firstnames(): void {
 
 		global $post, $coauthors_plus;
 
@@ -196,7 +196,7 @@ public function test_coauthors_firstnames() {
 	 * @covers ::coauthors_lastnames()
 	 * @covers ::coauthors__echo()
 	 */
-	public function test_coauthors_lastnames() {
+	public function test_coauthors_lastnames(): void {
 
 		global $post, $coauthors_plus;
 
@@ -251,7 +251,7 @@ public function test_coauthors_lastnames() {
 	 * @covers ::coauthors_nicknames()
 	 * @covers ::coauthors__echo()
 	 */
-	public function test_coauthors_nicknames() {
+	public function test_coauthors_nicknames(): void {
 
 		global $post, $coauthors_plus;
 
@@ -306,7 +306,7 @@ public function test_coauthors_nicknames() {
 	 * @covers ::coauthors_emails()
 	 * @covers ::coauthors__echo()
 	 */
-	public function test_coauthors_emails() {
+	public function test_coauthors_emails(): void {
 
 		global $post, $coauthors_plus;
 
@@ -358,7 +358,7 @@ public function test_coauthors_emails() {
 	 *
 	 * @covers ::coauthors_links_single()
 	 */
-	public function test_coauthors_links_single_when_guest_author() {
+	public function test_coauthors_links_single_when_guest_author(): void {
 
 		global $post, $authordata;
 
@@ -408,7 +408,7 @@ public function test_coauthors_links_single_when_guest_author() {
 	 *
 	 * @covers ::coauthors_links_single()
 	 */
-	public function test_coauthors_links_single_author_url_is_set() {
+	public function test_coauthors_links_single_author_url_is_set(): void {
 
 		global $post, $authordata;
 
@@ -449,7 +449,7 @@ public function test_coauthors_links_single_author_url_is_set() {
 	 *
 	 * @covers ::coauthors_links_single()
 	 */
-	public function test_coauthors_links_single_when_url_not_exist() {
+	public function test_coauthors_links_single_when_url_not_exist(): void {
 		global $wp_version;
 		if ( PHP_VERSION_ID >= 80100 && version_compare( $wp_version, '6.3.0', '<' ) ) {
 			/*
@@ -494,7 +494,7 @@ public function test_coauthors_links_single_when_url_not_exist() {
 	 * @covers ::coauthors_ids()
 	 * @covers ::coauthors__echo()
 	 */
-	public function test_coauthors_ids() {
+	public function test_coauthors_ids(): void {
 
 		global $post, $coauthors_plus;
 
@@ -530,7 +530,7 @@ public function test_coauthors_ids() {
 	 *
 	 * @covers ::get_the_coauthor_meta()
 	 */
-	public function test_get_the_coauthor_meta() {
+	public function test_get_the_coauthor_meta(): void {
 
 		global $post;
 

From 1109da9becced143b0db193ab12d99b43e70107d Mon Sep 17 00:00:00 2001
From: Gary Jones <gary.jones@automattic.com>
Date: Tue, 23 Apr 2024 16:48:50 +0100
Subject: [PATCH 8/9] PHP 7.4: Collapse nested dirname() calls

---
 tests/Integration/bootstrap.php | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tests/Integration/bootstrap.php b/tests/Integration/bootstrap.php
index 32aa881e..639f5c05 100644
--- a/tests/Integration/bootstrap.php
+++ b/tests/Integration/bootstrap.php
@@ -7,7 +7,7 @@
 
 use Yoast\WPTestUtils\WPIntegration;
 
-require_once dirname( dirname( __DIR__ ) ) . '/vendor/yoast/wp-test-utils/src/WPIntegration/bootstrap-functions.php';
+require_once dirname( __DIR__, 2 ) . '/vendor/yoast/wp-test-utils/src/WPIntegration/bootstrap-functions.php';
 
 $_tests_dir = getenv( 'WP_TESTS_DIR' );
 
@@ -34,7 +34,7 @@
  */
 function _manually_load_plugin() {
 	// Updated from default (__FILE__), since this bootstrap is an extra level down in tests/Integration/.
-	require dirname( dirname( __DIR__ ) ) . '/co-authors-plus.php';
+	require dirname( __DIR__, 2 ) . '/co-authors-plus.php';
 }
 
 tests_add_filter( 'muplugins_loaded', '_manually_load_plugin' );

From 947b3f2aa6edcaadec444cf826b1c096239ab422 Mon Sep 17 00:00:00 2001
From: Gary Jones <gary.jones@automattic.com>
Date: Tue, 23 Apr 2024 17:06:12 +0100
Subject: [PATCH 9/9] CI: Remove MySQL workaround for PHP <= 7.3

---
 .github/workflows/integrate.yml | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/.github/workflows/integrate.yml b/.github/workflows/integrate.yml
index ff3caa44..2b607191 100644
--- a/.github/workflows/integrate.yml
+++ b/.github/workflows/integrate.yml
@@ -67,10 +67,6 @@ jobs:
       - name: Start MySQL service
         run: sudo systemctl start mysql.service
 
-      - name: Setting mysql_native_password for PHP <= 7.3
-        if: ${{ matrix.php <= 7.3 }}
-        run: mysql -u root -proot -e "ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY 'root'";
-
       - name: Install WordPress environment
         run: composer prepare ${{ matrix.wordpress }}