diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 0630777..f87bfa3 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -12,11 +12,18 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php-versions: ['8.0', '8.1', '8.2']
+        php-versions: ['8.0', '8.1', '8.2', '8.3']
         coverage: ['xdebug']
+        code-style: ['yes']
         code-analysis: ['no']
         include:
           - php-versions: '7.4'
+            coverage: 'none'
+            code-style: 'yes'
+            code-analysis: 'yes'
+          - php-versions: '8.4'
+            coverage: 'xdebug'
+            code-style: 'yes'
             code-analysis: 'yes'
     steps:
       - name: Checkout
@@ -45,8 +52,8 @@ jobs:
         run: composer install --no-progress --prefer-dist --optimize-autoloader
 
       - name: Code Analysis (PHP CS-Fixer)
-        if: matrix.code-analysis == 'yes'
-        run: php vendor/bin/php-cs-fixer fix --dry-run --diff
+        if: matrix.code-style == 'yes'
+        run: PHP_CS_FIXER_IGNORE_ENV=true php vendor/bin/php-cs-fixer fix --dry-run --diff
 
       - name: Code Analysis (PHPStan)
         if: matrix.code-analysis == 'yes'
diff --git a/.php-cs-fixer.dist.php b/.php-cs-fixer.dist.php
index e981862..4d464eb 100644
--- a/.php-cs-fixer.dist.php
+++ b/.php-cs-fixer.dist.php
@@ -10,6 +10,10 @@
 $config->setRules([
     '@PSR1' => true,
     '@Symfony' => true,
+    'nullable_type_declaration' => [
+        'syntax' => 'question_mark',
+    ],
+    'nullable_type_declaration_for_default_null_value' => true,
 ]);
 
 return $config;
diff --git a/composer.json b/composer.json
index 0dc4761..8781e8a 100644
--- a/composer.json
+++ b/composer.json
@@ -13,8 +13,8 @@
         "sabre/uri"    : "^2.3"
     },
     "require-dev" : {
-        "friendsofphp/php-cs-fixer": "^3.54",
-        "phpstan/phpstan": "^1.10",
+        "friendsofphp/php-cs-fixer": "^3.64",
+        "phpstan/phpstan": "^1.12",
         "phpunit/phpunit" : "^9.6"
     },
     "suggest" : {
@@ -50,7 +50,7 @@
             "phpstan analyse lib tests"
         ],
         "cs-fixer": [
-            "php-cs-fixer fix"
+            "PHP_CS_FIXER_IGNORE_ENV=true php-cs-fixer fix"
         ],
         "phpunit": [
             "phpunit --configuration tests/phpunit.xml"
diff --git a/lib/Client.php b/lib/Client.php
index f94d933..22ec6f9 100644
--- a/lib/Client.php
+++ b/lib/Client.php
@@ -475,7 +475,7 @@ protected function parseCurlResponse(array $headerLines, string $body, $curlHand
         list(
             $curlInfo,
             $curlErrNo,
-            $curlErrMsg
+            $curlErrMsg,
         ) = $this->curlStuff($curlHandle);
 
         if ($curlErrNo) {
@@ -532,7 +532,7 @@ protected function parseCurlResult(string $response, $curlHandle): array
         list(
             $curlInfo,
             $curlErrNo,
-            $curlErrMsg
+            $curlErrMsg,
         ) = $this->curlStuff($curlHandle);
 
         if ($curlErrNo) {
diff --git a/lib/Response.php b/lib/Response.php
index 934d724..92baafd 100644
--- a/lib/Response.php
+++ b/lib/Response.php
@@ -153,7 +153,7 @@ public function setStatus($status): void
         } else {
             list(
                 $statusCode,
-                $statusText
+                $statusText,
             ) = explode(' ', $status, 2);
         }
         $statusCode = (int) $statusCode;
diff --git a/phpstan.neon b/phpstan.neon
index 5802f6f..4be9ef9 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -18,3 +18,7 @@ parameters:
     message: "#^Strict comparison using === between null and array<string, mixed> will always evaluate to false.$#"
     count: 1
     path: lib/functions.php
+  -
+    message: "#^Offset 'value' on array.* in isset\\(\\) always exists and is not nullable.$#"
+    count: 1
+    path: lib/functions.php