diff --git a/.travis.yml b/.travis.yml
index 71d2b3c..4a64b2f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,11 +8,10 @@ branches:
 
 matrix:
   include:
-    - php: 7.1
+    - php: 7.3
       env: dependencies=highest
-    - php: 7.0.11
-    - php: 5.6
-    - php: 5.5
+    - php: 7.2
+    - php: 7.1
       env: dependencies=lowest
 
 sudo: false
diff --git a/src/Runner.php b/src/Runner.php
index 26d3225..ef011ab 100644
--- a/src/Runner.php
+++ b/src/Runner.php
@@ -43,22 +43,42 @@ public function start( $target_dir, $opts ) {
 		}
 
 		// Determine whether there is an existing open PR with Composer updates
-		$existing_PR_branch = $this->checkExisting();
+		$existing_PR_branch = $this->checkExistingPRBranch();
 
 		if ( $existing_PR_branch ) {
-			Logger::info( "Using existing branch: $existing_PR_branch" );
+			exec( 'git rev-parse --abbrev-ref HEAD', $initial_branch, $return_code );
+			if ( 0 !== $return_code ) {
+				Logger::error( 'Failed to fetch initial branch.' );
+			}
+			$initial_branch = $initial_branch[0];
+			Logger::info( "Inspecting existing branch: $existing_PR_branch" );
 			passthru( 'git fetch' );
 			passthru( 'git checkout ' . $existing_PR_branch );
+			// Check to see if there are any outdated dependencies.
+			$this->runComposerInstall();
+			exec( 'composer outdated', $output, $return_code );
+			if ( 0 !== $return_code ) {
+				Logger::error( 'Failed to run composer outdated.' );
+			}
+			if ( empty( $output ) ) {
+				Logger::info('Exiting since no updates were detected on existing PR branch.');
+				exit(0);
+			}
+			// Close the existing PR and delete its branch.
+			$this->closeExistingPRBranch( $existing_PR_branch );
+			// Check out the initial branch locally and delete the local PR branch.
+			passthru( 'git checkout ' . $initial_branch );
+			$cmd = 'git branch -D ' . escapeshellarg( $existing_PR_branch );
+			Logger::info( $cmd );
+			passthru( $cmd, $return_code );
+			if ( 0 !== $return_code ) {
+				Logger::error( 'Failed to delete local branch.' );
+			}
+			// Fall through to create the new branch.
 		}
 
 		// Perform an initial install to sanity check the package.
-		$args = getenv( 'CLU_COMPOSER_INSTALL_ARGS' ) ? : '--no-dev --no-interaction';
-		$cmd  = 'composer install ' . $args;
-		Logger::info( $cmd );
-		passthru( $cmd, $return_code );
-		if ( 0 !== $return_code ) {
-			Logger::error( 'Composer failed to install dependencies.' );
-		}
+		$this->runComposerInstall();
 
 		$cmd = 'composer outdated';
 		Logger::info( $cmd );
@@ -121,16 +141,13 @@ public function start( $target_dir, $opts ) {
 		Logger::info( 'Set git config name and email.' );
 
 		$date = date( 'Y-m-d-H-i' );
-		$branch_name = $existing_PR_branch;
-		if ( !$existing_PR_branch ) {
-			// Checkout a dated branch to make the commit
-			$branch_name = 'clu-' . $date;
-			$cmd = 'git checkout -b ' . escapeshellarg( $branch_name );
-			Logger::info( $cmd );
-			passthru( $cmd, $return_code );
-			if ( 0 !== $return_code ) {
-				Logger::error( 'Failed to check out branch.' );
-			}
+		// Checkout a dated branch to make the commit
+		$branch_name = 'clu-' . $date;
+		$cmd = 'git checkout -b ' . escapeshellarg( $branch_name );
+		Logger::info( $cmd );
+		passthru( $cmd, $return_code );
+		if ( 0 !== $return_code ) {
+			Logger::error( 'Failed to check out branch.' );
 		}
 
 		$message = <<<EOT
@@ -155,13 +172,6 @@ public function start( $target_dir, $opts ) {
 			Logger::error( 'Failed to push changes to origin.' );
 		}
 
-		if ( $existing_PR_branch && $this->isGitLab() ) {
-			// Add comment to existing PR with $message
-			$commitSha = exec( 'git rev-parse HEAD', $output_lines, $return_code);
-			$this->addCommitComment( $message, $this->project(), $commitSha );
-			Logger::success( sprintf( 'Updated %s with composer.lock changes.', $this->getRequestType() ) );
-			return;
-		}
 		if ( $this->isGitHub() ) {
 			$cmd = 'hub pull-request -m ' . escapeshellarg( $message );
 		} elseif ( $this->isGitLab() ) {
@@ -176,7 +186,7 @@ public function start( $target_dir, $opts ) {
 		Logger::success( sprintf( 'Created %s with composer.lock changes.', $this->getRequestType() ) );
 	}
 
-	private function checkExisting() {
+	private function checkExistingPRBranch() {
 		if ( $this->isGitHub() ) {
 			$cmd = 'hub pr list --format="%t%n" --state=open';
 		} elseif ( $this->isGitLab() ) {
@@ -197,6 +207,50 @@ private function checkExisting() {
 		return false;
 	}
 
+	/**
+	 * Closes an existing PR branch.
+	 *
+	 * @param string $branch_name Name of the branch.
+	 * @return boolean
+	 */
+	private function closeExistingPRBranch( $branch_name ) {
+		if ( $this->isGitHub() ) {
+			$cmd = 'hub pr list --format="%i" --state=open';
+		} elseif ( $this->isGitLab() ) {
+			$cmd = 'lab mr list';
+		} else {
+			return false;
+		}
+		exec($cmd, $output_lines, $return_code);
+		if ( 0 !== $return_code ) {
+			Logger::error( sprintf( 'Unable to check for existing %ss', $this->getRequestType() ) );
+		}
+		$number = false;
+		foreach( $output_lines as $line ) {
+			if ( preg_match( '/^\#([\d]+)/', $line, $matches ) ) {
+				$number = $matches[1];
+			}
+		}
+		if ( ! $number ) {
+			Logger::error( sprintf( 'Unable to find existing %s number', $this->getRequestType() ) );
+		}
+		if ( $this->isGitHub() ) {
+			$cmd = sprintf( 'hub api -XPATCH repos/%s/issues/%d -f state=closed', $this->project(), $number );
+		} elseif ( $this->isGitLab() ) {
+			$cmd = sprintf( 'lab mr close %d', $number );
+		}
+		exec($cmd, $output_lines, $return_code);
+		if ( 0 !== $return_code ) {
+			Logger::error( sprintf( 'Unable to close existing %s', $this->getRequestType() ) );
+		}
+		$cmd = 'git push origin --delete ' . escapeshellarg( $branch_name );
+		Logger::info( $cmd );
+		passthru( $cmd, $return_code );
+		if ( 0 !== $return_code ) {
+			Logger::error( 'Failed to delete origin branch.' );
+		}
+	}
+
 	/**
 	 * Check the Sensiolabs security component if availble.
 	 *
@@ -243,102 +297,22 @@ private function getRequestType() {
 		return $this->isGitLab() ? 'merge request' : 'pull request';
 	}
 
-	private function addCommitComment( $message, $project, $commitSha ) {
-		// We expect that GITHUB token should always be defined; however, we
-		// will silently omit the comment if it is not, since the new commit
-		// is already visible on the PR, and the separate comment is therefore
-		// not necessary for correct operation.
-		$auth = getenv( 'GITHUB_TOKEN' );
-		if ( !$auth ) {
-			return;
-		}
-
-		$uri = "repos/$project/commits/$commitSha/comments";
-		$data = [
-			'body' => $message,
-		];
-
-		$this->curlGitHub($uri, $data, $auth);
-	}
-
-	public function curlGitHub( $uri, $postData = [], $auth = '' ) {
-		Logger::info( 'Call GitHub API: ' . $uri );
-		$ch = $this->createGitHubPostChannel( $uri, $postData, $auth );
-		return $this->execCurlRequest( $ch, 'GitHub' );
-	}
-
-	protected function createGitHubPostChannel( $uri, $postData = [], $auth = '' ) {
-		$url = "https://api.github.com/$uri";
-		$ch = $this->createAuthorizationHeaderCurlChannel( $url, $auth );
-		$this->setCurlChannelPostData( $ch, $postData );
-
-		return $ch;
-	}
-
-	protected function createAuthorizationHeaderCurlChannel( $url, $auth = '' ) {
-		$headers = [
-			'Content-Type: application/json',
-			'User-Agent: pantheon/terminus-build-tools-plugin'
-		];
-
-		if (!empty($auth)) {
-			$headers[] = "Authorization: token $auth";
-		}
-
-		$ch = curl_init();
-		curl_setopt( $ch, CURLOPT_URL, $url );
-		curl_setopt( $ch, CURLOPT_RETURNTRANSFER, 1 );
-		curl_setopt( $ch, CURLOPT_TIMEOUT, 5 );
-		curl_setopt( $ch, CURLOPT_HTTPHEADER, $headers );
-
-		return $ch;
-	}
-
-	protected function setCurlChannelPostData( $ch, $postData, $force = false ) {
-		if ( !empty($postData) || $force ) {
-			$payload = json_encode( $postData );
-			curl_setopt( $ch, CURLOPT_POST, 1 );
-			curl_setopt( $ch, CURLOPT_POSTFIELDS, $payload );
-		}
-	}
-
-	public function execCurlRequest( $ch, $service = 'API request' ) {
-		$result = curl_exec($ch);
-		if( curl_errno($ch) )
-		{
-			Logger::error( curl_error($ch) );
-		}
-		$data = json_decode( $result, true );
-		$httpCode = curl_getinfo( $ch, CURLINFO_HTTP_CODE );
-		curl_close( $ch );
-
-		$errors = [];
-		if ( isset($data['errors']) ) {
-			foreach ( $data['errors'] as $error ) {
-				$errors[] = $error['message'];
-			}
-		}
-		if ( $httpCode && ($httpCode >= 300) ) {
-			$errors[] = "Http status code: $httpCode";
-		}
-
-		$message = isset( $data['message'] ) ? "{$data['message']}." : '';
-
-		if ( !empty($message) || !empty($errors) ) {
-			  $errors = implode( "\n", $errors );
-			Logger::error( "$service error: $message $errors" );
+	/**
+	 * Runs `composer install`.
+	 */
+	private function runComposerInstall() {
+		$args = getenv( 'CLU_COMPOSER_INSTALL_ARGS' ) ? : '--no-dev --no-interaction';
+		$cmd  = 'composer install ' . $args;
+		Logger::info( $cmd );
+		passthru( $cmd, $return_code );
+		if ( 0 !== $return_code ) {
+			Logger::error( 'Composer failed to install dependencies.' );
 		}
-
-		return $data;
-	}
-
-	private function repo() {
-		return $this->repo_url;
 	}
 
 	private function project() {
 		if ( preg_match( '#([^/:]*/.*)$#', $this->repo_url, $matches ) ) {
-			return rtrim( $matches[1], '.git' );
+			return preg_replace( '#\.git$#', '', $matches[1] );
 		}
 	}