Coding Standards: Use static closures when not using $this.

When a closure does not use `$this`, it can be made `static` for improved performance.

Static closures are supported in PHP since PHP 5.4. ​

Props jrf, hellofromTonya, swissspidy, SergeyBiryukov.
See #53359.

git-svn-id: https://develop.svn.wordpress.org/trunk@51657 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/edit-form-blocks.php

@@ -31,7 +31,7 @@ $current_screen->is_block_editor( true );
 // Default to is-fullscreen-mode to avoid jumps in the UI.
 add_filter(
 	'admin_body_class',
-	function( $classes ) {
+	static function( $classes ) {
 		return "$classes is-fullscreen-mode";
 	}
 );

src/wp-admin/includes/class-wp-community-events.php

@@ -474,7 +474,7 @@ class WP_Community_Events {
 
 		$future_wordcamps = array_filter(
 			$future_events,
-			function( $wordcamp ) {
+			static function( $wordcamp ) {
 				return 'wordcamp' === $wordcamp['type'];
 			}
 		);

src/wp-admin/includes/class-wp-site-health-auto-updates.php

@@ -41,7 +41,7 @@ class WP_Site_Health_Auto_Updates {
 
 		$tests = array_filter( $tests );
 		$tests = array_map(
-			function( $test ) {
+			static function( $test ) {
 				$test = (object) $test;
 
 				if ( empty( $test->severity ) ) {

src/wp-admin/includes/update-core.php

@@ -1658,7 +1658,7 @@ function _upgrade_422_find_genericons_files_in_folder( $directory ) {
 	$dirs = glob( $directory . '*', GLOB_ONLYDIR );
 	$dirs = array_filter(
 		$dirs,
-		function( $dir ) {
+		static function( $dir ) {
 			// Skip any node_modules directories.
 			return false === strpos( $dir, 'node_modules' );
 		}

src/wp-admin/options-privacy.php

@@ -20,7 +20,7 @@ if ( isset( $_GET['tab'] ) && 'policyguide' === $_GET['tab'] ) {
 
 add_filter(
 	'admin_body_class',
-	function( $body_class ) {
+	static function( $body_class ) {
 		$body_class .= ' privacy-settings ';
 
 		return $body_class;

src/wp-admin/privacy-policy-guide.php

@@ -19,7 +19,7 @@ if ( ! class_exists( 'WP_Privacy_Policy_Content' ) ) {
 
 add_filter(
 	'admin_body_class',
-	function( $body_class ) {
+	static function( $body_class ) {
 		$body_class .= ' privacy-settings ';
 
 		return $body_class;