Plugins: Improve hook performance by using spl_object_id() instead of spl_object_hash() to construct unique IDs.

* Also use `spl_object_id()` similarly when registering and unregistering classic widgets.
* Improve typing and phpdoc in `_wp_filter_build_unique_id()`. Return `null` for malformed callbacks.
* Add tests for `_wp_filter_build_unique_id()`.
* Improve type safety of `WP_Hook::add_filter()` in case an invalid callback is provided for parity with `::has_filter()` and `::remove_filter()`.

Developed in WordPress#11865
Follow-up to r46220, r46801, r60179.

Props bor0, westonruter, SergeyBiryukov, schlessera, arshidkv12, knutsp, spacedmonkey, swissspidy.
See #64898.
Fixes #58291.


git-svn-id: https://develop.svn.wordpress.org/trunk@62408 602fd350-edb4-49c9-b593-d223f7449a82

Author: westonruter

src/wp-includes/class-wp-hook.php

@@ -85,6 +85,9 @@ public function add_filter( $hook_name, $callback, $priority, $accepted_args ) {
 		}
 
 		$idx = _wp_filter_build_unique_id( $hook_name, $callback, $priority );
+		if ( null === $idx ) {
+			return;
+		}
 
 		$priority_existed = isset( $this->callbacks[ $priority ] );
 

src/wp-includes/class-wp-widget-factory.php

@@ -57,7 +57,7 @@ public function WP_Widget_Factory() {
 	 */
 	public function register( $widget ) {
 		if ( $widget instanceof WP_Widget ) {
-			$this->widgets[ spl_object_hash( $widget ) ] = $widget;
+			$this->widgets[ spl_object_id( $widget ) ] = $widget;
 		} else {
 			$this->widgets[ $widget ] = new $widget();
 		}
@@ -74,7 +74,7 @@ public function register( $widget ) {
 	 */
 	public function unregister( $widget ) {
 		if ( $widget instanceof WP_Widget ) {
-			unset( $this->widgets[ spl_object_hash( $widget ) ] );
+			unset( $this->widgets[ spl_object_id( $widget ) ] );
 		} else {
 			unset( $this->widgets[ $widget ] );
 		}

src/wp-includes/plugin.php

@@ -986,33 +986,36 @@ function _wp_call_all_hook( $args ) {
  * @since 2.2.3
  * @since 5.3.0 Removed workarounds for spl_object_hash().
  *              `$hook_name` and `$priority` are no longer used,
- *              and the function always returns a string.
+ *              and no longer returns false, but can still return void for invalid callbacks.
+ * @since 6.9.0 Returns explicit null if an invalid callback is supplied.
+ * @since 7.1.0 Uses spl_object_id() instead of spl_object_hash() for performance.
  *
  * @access private
  *
- * @param string                $hook_name Unused. The name of the filter to build ID for.
- * @param callable|string|array $callback  The callback to generate ID for. The callback may
- *                                         or may not exist.
- * @param int                   $priority  Unused. The order in which the functions
- *                                         associated with a particular action are executed.
- * @return string|null Unique function ID for usage as array key.
- *                     Null if a valid `$callback` is not passed.
+ * @param string   $hook_name Unused. The name of the filter to build ID for.
+ * @param callable $callback  The callback to generate ID for. The callback may
+ *                            or may not exist.
+ * @param int      $priority  Unused. The order in which the functions
+ *                            associated with a particular action are executed.
+ * @return string|null Unique function ID for usage as array key, or null if it couldn't be determined.
  */
-function _wp_filter_build_unique_id( $hook_name, $callback, $priority ) {
+function _wp_filter_build_unique_id( $hook_name, $callback, $priority ): ?string {
 	if ( is_string( $callback ) ) {
 		return $callback;
 	}
 
 	if ( is_object( $callback ) ) {
-		// Closures are currently implemented as objects.
-		$callback = array( $callback, '' );
-	} else {
-		$callback = (array) $callback;
+		return (string) spl_object_id( (object) $callback );
+	}
+
+	$callback = (array) $callback;
+	if ( ! isset( $callback[1] ) || ! is_string( $callback[1] ) ) {
+		return null;
 	}
 
 	if ( is_object( $callback[0] ) ) {
 		// Object class calling.
-		return spl_object_hash( $callback[0] ) . $callback[1];
+		return ( (string) spl_object_id( $callback[0] ) ) . $callback[1];
 	} elseif ( is_string( $callback[0] ) ) {
 		// Static calling.
 		return $callback[0] . '::' . $callback[1];

tests/phpunit/tests/hooks/buildUniqueId.php

@@ -0,0 +1,62 @@
+<?php
+
+/**
+ * Tests for _wp_filter_build_unique_id().
+ *
+ * @group hooks
+ * @covers ::_wp_filter_build_unique_id
+ */
+class Tests_Hooks_BuildUniqueId extends WP_UnitTestCase {
+
+	public function test_string_callback_returns_string(): void {
+		$result = _wp_filter_build_unique_id( '', '__return_null', 10 );
+		$this->assertIsString( $result );
+		$this->assertSame( '__return_null', $result );
+	}
+
+	public function test_closure_returns_string(): void {
+		$cb     = function (): void {};
+		$result = _wp_filter_build_unique_id( '', $cb, 10 );
+		$this->assertIsString( $result );
+	}
+
+	public function test_object_callback_returns_string(): void {
+		$a      = new MockAction();
+		$result = _wp_filter_build_unique_id( '', array( $a, 'action' ), 10 );
+		$this->assertIsString( $result );
+	}
+
+	public function test_static_callback_returns_string(): void {
+		$result = _wp_filter_build_unique_id( '', array( 'MockAction', 'action' ), 10 );
+		$this->assertIsString( $result );
+	}
+
+	public function test_two_different_objects_produce_different_ids(): void {
+		$a = new MockAction();
+		$b = new MockAction();
+		$this->assertNotSame(
+			_wp_filter_build_unique_id( '', array( $a, 'action' ), 10 ),
+			_wp_filter_build_unique_id( '', array( $b, 'action' ), 10 )
+		);
+	}
+
+	public function test_same_object_produces_same_id(): void {
+		$a = new MockAction();
+		$this->assertSame(
+			_wp_filter_build_unique_id( '', array( $a, 'action' ), 10 ),
+			_wp_filter_build_unique_id( '', array( $a, 'action' ), 10 )
+		);
+	}
+
+	public function test_malformed_array_missing_method_returns_null(): void {
+		$a      = new MockAction();
+		$result = _wp_filter_build_unique_id( '', array( $a ), 10 );
+		$this->assertNull( $result );
+	}
+
+	public function test_malformed_array_non_string_method_returns_null(): void {
+		$a      = new MockAction();
+		$result = _wp_filter_build_unique_id( '', array( $a, 123 ), 10 );
+		$this->assertNull( $result );
+	}
+}