1<?php
  2/**
  3 * Plugin API: WP_Hook class
  4 *
  5 * @package WordPress
  6 * @subpackage Plugin
  7 * @since 4.7.0
  8 */
  9
 10/**
 11 * Core class used to implement action and filter hook functionality.
 12 *
 13 * @since 4.7.0
 14 *
 15 * @see Iterator
 16 * @see ArrayAccess
 17 */
 18#[AllowDynamicProperties]
 19final class WP_Hook implements Iterator, ArrayAccess {
 20
 21	/**
 22	 * Hook callbacks.
 23	 *
 24	 * @since 4.7.0
 25	 * @var array
 26	 */
 27	public $callbacks = array();
 28
 29	/**
 30	 * Priorities list.
 31	 *
 32	 * @since 6.4.0
 33	 * @var array
 34	 */
 35	protected $priorities = array();
 36
 37	/**
 38	 * The priority keys of actively running iterations of a hook.
 39	 *
 40	 * @since 4.7.0
 41	 * @var array
 42	 */
 43	private $iterations = array();
 44
 45	/**
 46	 * The current priority of actively running iterations of a hook.
 47	 *
 48	 * @since 4.7.0
 49	 * @var array
 50	 */
 51	private $current_priority = array();
 52
 53	/**
 54	 * Number of levels this hook can be recursively called.
 55	 *
 56	 * @since 4.7.0
 57	 * @var int
 58	 */
 59	private $nesting_level = 0;
 60
 61	/**
 62	 * Flag for if we're currently doing an action, rather than a filter.
 63	 *
 64	 * @since 4.7.0
 65	 * @var bool
 66	 */
 67	private $doing_action = false;
 68
 69	/**
 70	 * Adds a callback function to a filter hook.
 71	 *
 72	 * @since 4.7.0
 73	 *
 74	 * @param string   $hook_name     The name of the filter to add the callback to.
 75	 * @param callable $callback      The callback to be run when the filter is applied.
 76	 * @param int      $priority      The order in which the functions associated with a particular filter
 77	 *                                are executed. Lower numbers correspond with earlier execution,
 78	 *                                and functions with the same priority are executed in the order
 79	 *                                in which they were added to the filter.
 80	 * @param int      $accepted_args The number of arguments the function accepts.
 81	 */
 82	public function add_filter( $hook_name, $callback, $priority, $accepted_args ) {
 83		if ( null === $priority ) {
 84			$priority = 0;
 85		}
 86
 87		$idx = _wp_filter_build_unique_id( $hook_name, $callback, $priority );
 88
 89		$priority_existed = isset( $this->callbacks[ $priority ] );
 90
 91		$this->callbacks[ $priority ][ $idx ] = array(
 92			'function'      => $callback,
 93			'accepted_args' => (int) $accepted_args,
 94		);
 95
 96		// If we're adding a new priority to the list, put them back in sorted order.
 97		if ( ! $priority_existed && count( $this->callbacks ) > 1 ) {
 98			ksort( $this->callbacks, SORT_NUMERIC );
 99		}
100
101		$this->priorities = array_keys( $this->callbacks );
102
103		if ( $this->nesting_level > 0 ) {
104			$this->resort_active_iterations( $priority, $priority_existed );
105		}
106	}
107
108	/**
109	 * Handles resetting callback priority keys mid-iteration.
110	 *
111	 * @since 4.7.0
112	 *
113	 * @param false|int $new_priority     Optional. The priority of the new filter being added. Default false,
114	 *                                    for no priority being added.
115	 * @param bool      $priority_existed Optional. Flag for whether the priority already existed before the new
116	 *                                    filter was added. Default false.
117	 */
118	private function resort_active_iterations( $new_priority = false, $priority_existed = false ) {
119		$new_priorities = $this->priorities;
120
121		// If there are no remaining hooks, clear out all running iterations.
122		if ( ! $new_priorities ) {
123			foreach ( $this->iterations as $index => $iteration ) {
124				$this->iterations[ $index ] = $new_priorities;
125			}
126
127			return;
128		}
129
130		$min = min( $new_priorities );
131
132		foreach ( $this->iterations as $index => &$iteration ) {
133			$current = current( $iteration );
134
135			// If we're already at the end of this iteration, just leave the array pointer where it is.
136			if ( false === $current ) {
137				continue;
138			}
139
140			$iteration = $new_priorities;
141
142			if ( $current < $min ) {
143				array_unshift( $iteration, $current );
144				continue;
145			}
146
147			while ( current( $iteration ) < $current ) {
148				if ( false === next( $iteration ) ) {
149					break;
150				}
151			}
152
153			// If we have a new priority that didn't exist, but ::apply_filters() or ::do_action() thinks it's the current priority...
154			if ( $new_priority === $this->current_priority[ $index ] && ! $priority_existed ) {
155				/*
156				 * ...and the new priority is the same as what $this->iterations thinks is the previous
157				 * priority, we need to move back to it.
158				 */
159
160				if ( false === current( $iteration ) ) {
161					// If we've already moved off the end of the array, go back to the last element.
162					$prev = end( $iteration );
163				} else {
164					// Otherwise, just go back to the previous element.
165					$prev = prev( $iteration );
166				}
167
168				if ( false === $prev ) {
169					// Start of the array. Reset, and go about our day.
170					reset( $iteration );
171				} elseif ( $new_priority !== $prev ) {
172					// Previous wasn't the same. Move forward again.
173					next( $iteration );
174				}
175			}
176		}
177
178		unset( $iteration );
179	}
180
181	/**
182	 * Removes a callback function from a filter hook.
183	 *
184	 * @since 4.7.0
185	 *
186	 * @param string                $hook_name The filter hook to which the function to be removed is hooked.
187	 * @param callable|string|array $callback  The callback to be removed from running when the filter is applied.
188	 *                                         This method can be called unconditionally to speculatively remove
189	 *                                         a callback that may or may not exist.
190	 * @param int                   $priority  The exact priority used when adding the original filter callback.
191	 * @return bool Whether the callback existed before it was removed.
192	 */
193	public function remove_filter( $hook_name, $callback, $priority ) {
194		if ( null === $priority ) {
195			$priority = 0;
196		}
197
198		$function_key = _wp_filter_build_unique_id( $hook_name, $callback, $priority );
199
200		$exists = isset( $function_key, $this->callbacks[ $priority ][ $function_key ] );
201
202		if ( $exists ) {
203			unset( $this->callbacks[ $priority ][ $function_key ] );
204
205			if ( ! $this->callbacks[ $priority ] ) {
206				unset( $this->callbacks[ $priority ] );
207
208				$this->priorities = array_keys( $this->callbacks );
209
210				if ( $this->nesting_level > 0 ) {
211					$this->resort_active_iterations();
212				}
213			}
214		}
215
216		return $exists;
217	}
218
219	/**
220	 * Checks if a specific callback has been registered for this hook.
221	 *
222	 * When using the `$callback` argument, this function may return a non-boolean value
223	 * that evaluates to false (e.g. 0), so use the `===` operator for testing the return value.
224	 *
225	 * @since 4.7.0
226	 * @since 6.9.0 Added the `$priority` parameter.
227	 *
228	 * @param string                      $hook_name Optional. The name of the filter hook. Default empty.
229	 * @param callable|string|array|false $callback  Optional. The callback to check for.
230	 *                                               This method can be called unconditionally to speculatively check
231	 *                                               a callback that may or may not exist. Default false.
232	 * @param int|false                   $priority  Optional. The specific priority at which to check for the callback.
233	 *                                               Default false.
234	 * @return bool|int If `$callback` is omitted, returns boolean for whether the hook has
235	 *                  anything registered. When checking a specific function, the priority
236	 *                  of that hook is returned, or false if the function is not attached.
237	 *                  If `$callback` and `$priority` are both provided, a boolean is returned
238	 *                  for whether the specific function is registered at that priority.
239	 */
240	public function has_filter( $hook_name = '', $callback = false, $priority = false ) {
241		if ( false === $callback ) {
242			return $this->has_filters();
243		}
244
245		$function_key = _wp_filter_build_unique_id( $hook_name, $callback, false );
246
247		if ( ! $function_key ) {
248			return false;
249		}
250
251		if ( is_int( $priority ) ) {
252			return isset( $this->callbacks[ $priority ][ $function_key ] );
253		}
254
255		foreach ( $this->callbacks as $callback_priority => $callbacks ) {
256			if ( isset( $callbacks[ $function_key ] ) ) {
257				return $callback_priority;
258			}
259		}
260
261		return false;
262	}
263
264	/**
265	 * Checks if any callbacks have been registered for this hook.
266	 *
267	 * @since 4.7.0
268	 *
269	 * @return bool True if callbacks have been registered for the current hook, otherwise false.
270	 */
271	public function has_filters() {
272		foreach ( $this->callbacks as $callbacks ) {
273			if ( $callbacks ) {
274				return true;
275			}
276		}
277
278		return false;
279	}
280
281	/**
282	 * Removes all callbacks from the current filter.
283	 *
284	 * @since 4.7.0
285	 *
286	 * @param int|false $priority Optional. The priority number to remove. Default false.
287	 */
288	public function remove_all_filters( $priority = false ) {
289		if ( ! $this->callbacks ) {
290			return;
291		}
292
293		if ( false === $priority ) {
294			$this->callbacks  = array();
295			$this->priorities = array();
296		} elseif ( isset( $this->callbacks[ $priority ] ) ) {
297			unset( $this->callbacks[ $priority ] );
298			$this->priorities = array_keys( $this->callbacks );
299		}
300
301		if ( $this->nesting_level > 0 ) {
302			$this->resort_active_iterations();
303		}
304	}
305
306	/**
307	 * Calls the callback functions that have been added to a filter hook.
308	 *
309	 * @since 4.7.0
310	 *
311	 * @param mixed $value The value to filter.
312	 * @param array $args  Additional parameters to pass to the callback functions.
313	 *                     This array is expected to include $value at index 0.
314	 * @return mixed The filtered value after all hooked functions are applied to it.
315	 */
316	public function apply_filters( $value, $args ) {
317		if ( ! $this->callbacks ) {
318			return $value;
319		}
320
321		$nesting_level = $this->nesting_level++;
322
323		$this->iterations[ $nesting_level ] = $this->priorities;
324
325		$num_args = count( $args );
326
327		do {
328			$this->current_priority[ $nesting_level ] = current( $this->iterations[ $nesting_level ] );
329
330			$priority = $this->current_priority[ $nesting_level ];
331
332			foreach ( $this->callbacks[ $priority ] as $the_ ) {
333				if ( ! $this->doing_action ) {
334					$args[0] = $value;
335				}
336
337				// Avoid the array_slice() if possible.
338				if ( 0 === $the_['accepted_args'] ) {
339					$value = call_user_func( $the_['function'] );
340				} elseif ( $the_['accepted_args'] >= $num_args ) {
341					$value = call_user_func_array( $the_['function'], $args );
342				} else {
343					$value = call_user_func_array( $the_['function'], array_slice( $args, 0, $the_['accepted_args'] ) );
344				}
345			}
346		} while ( false !== next( $this->iterations[ $nesting_level ] ) );
347
348		unset( $this->iterations[ $nesting_level ] );
349		unset( $this->current_priority[ $nesting_level ] );
350
351		--$this->nesting_level;
352
353		return $value;
354	}
355
356	/**
357	 * Calls the callback functions that have been added to an action hook.
358	 *
359	 * @since 4.7.0
360	 *
361	 * @param array $args Parameters to pass to the callback functions.
362	 */
363	public function do_action( $args ) {
364		$this->doing_action = true;
365		$this->apply_filters( '', $args );
366
367		// If there are recursive calls to the current action, we haven't finished it until we get to the last one.
368		if ( ! $this->nesting_level ) {
369			$this->doing_action = false;
370		}
371	}
372
373	/**
374	 * Processes the functions hooked into the 'all' hook.
375	 *
376	 * @since 4.7.0
377	 *
378	 * @param array $args Arguments to pass to the hook callbacks. Passed by reference.
379	 */
380	public function do_all_hook( &$args ) {
381		$nesting_level                      = $this->nesting_level++;
382		$this->iterations[ $nesting_level ] = $this->priorities;
383
384		do {
385			$priority = current( $this->iterations[ $nesting_level ] );
386
387			foreach ( $this->callbacks[ $priority ] as $the_ ) {
388				call_user_func_array( $the_['function'], $args );
389			}
390		} while ( false !== next( $this->iterations[ $nesting_level ] ) );
391
392		unset( $this->iterations[ $nesting_level ] );
393		--$this->nesting_level;
394	}
395
396	/**
397	 * Return the current priority level of the currently running iteration of the hook.
398	 *
399	 * @since 4.7.0
400	 *
401	 * @return int|false If the hook is running, return the current priority level.
402	 *                   If it isn't running, return false.
403	 */
404	public function current_priority() {
405		if ( false === current( $this->iterations ) ) {
406			return false;
407		}
408
409		return current( current( $this->iterations ) );
410	}
411
412	/**
413	 * Normalizes filters set up before WordPress has initialized to WP_Hook objects.
414	 *
415	 * The `$filters` parameter should be an array keyed by hook name, with values
416	 * containing either:
417	 *
418	 *  - A `WP_Hook` instance
419	 *  - An array of callbacks keyed by their priorities
420	 *
421	 * Examples:
422	 *
423	 *     $filters = array(
424	 *         'wp_fatal_error_handler_enabled' => array(
425	 *             10 => array(
426	 *                 array(
427	 *                     'accepted_args' => 0,
428	 *                     'function'      => function() {
429	 *                         return false;
430	 *                     },
431	 *                 ),
432	 *             ),
433	 *         ),
434	 *     );
435	 *
436	 * @since 4.7.0
437	 *
438	 * @param array $filters Filters to normalize. See documentation above for details.
439	 * @return WP_Hook[] Array of normalized filters.
440	 */
441	public static function build_preinitialized_hooks( $filters ) {
442		/** @var WP_Hook[] $normalized */
443		$normalized = array();
444
445		foreach ( $filters as $hook_name => $callback_groups ) {
446			if ( $callback_groups instanceof WP_Hook ) {
447				$normalized[ $hook_name ] = $callback_groups;
448				continue;
449			}
450
451			$hook = new WP_Hook();
452
453			// Loop through callback groups.
454			foreach ( $callback_groups as $priority => $callbacks ) {
455
456				// Loop through callbacks.
457				foreach ( $callbacks as $cb ) {
458					$hook->add_filter( $hook_name, $cb['function'], $priority, $cb['accepted_args'] );
459				}
460			}
461
462			$normalized[ $hook_name ] = $hook;
463		}
464
465		return $normalized;
466	}
467
468	/**
469	 * Determines whether an offset value exists.
470	 *
471	 * @since 4.7.0
472	 *
473	 * @link https://www.php.net/manual/en/arrayaccess.offsetexists.php
474	 *
475	 * @param mixed $offset An offset to check for.
476	 * @return bool True if the offset exists, false otherwise.
477	 */
478	#[ReturnTypeWillChange]
479	public function offsetExists( $offset ) {
480		return isset( $this->callbacks[ $offset ] );
481	}
482
483	/**
484	 * Retrieves a value at a specified offset.
485	 *
486	 * @since 4.7.0
487	 *
488	 * @link https://www.php.net/manual/en/arrayaccess.offsetget.php
489	 *
490	 * @param mixed $offset The offset to retrieve.
491	 * @return mixed If set, the value at the specified offset, null otherwise.
492	 */
493	#[ReturnTypeWillChange]
494	public function offsetGet( $offset ) {
495		return isset( $this->callbacks[ $offset ] ) ? $this->callbacks[ $offset ] : null;
496	}
497
498	/**
499	 * Sets a value at a specified offset.
500	 *
501	 * @since 4.7.0
502	 *
503	 * @link https://www.php.net/manual/en/arrayaccess.offsetset.php
504	 *
505	 * @param mixed $offset The offset to assign the value to.
506	 * @param mixed $value The value to set.
507	 */
508	#[ReturnTypeWillChange]
509	public function offsetSet( $offset, $value ) {
510		if ( is_null( $offset ) ) {
511			$this->callbacks[] = $value;
512		} else {
513			$this->callbacks[ $offset ] = $value;
514		}
515
516		$this->priorities = array_keys( $this->callbacks );
517	}
518
519	/**
520	 * Unsets a specified offset.
521	 *
522	 * @since 4.7.0
523	 *
524	 * @link https://www.php.net/manual/en/arrayaccess.offsetunset.php
525	 *
526	 * @param mixed $offset The offset to unset.
527	 */
528	#[ReturnTypeWillChange]
529	public function offsetUnset( $offset ) {
530		unset( $this->callbacks[ $offset ] );
531		$this->priorities = array_keys( $this->callbacks );
532	}
533
534	/**
535	 * Returns the current element.
536	 *
537	 * @since 4.7.0
538	 *
539	 * @link https://www.php.net/manual/en/iterator.current.php
540	 *
541	 * @return array Of callbacks at current priority.
542	 */
543	#[ReturnTypeWillChange]
544	public function current() {
545		return current( $this->callbacks );
546	}
547
548	/**
549	 * Moves forward to the next element.
550	 *
551	 * @since 4.7.0
552	 *
553	 * @link https://www.php.net/manual/en/iterator.next.php
554	 *
555	 * @return array Of callbacks at next priority.
556	 */
557	#[ReturnTypeWillChange]
558	public function next() {
559		return next( $this->callbacks );
560	}
561
562	/**
563	 * Returns the key of the current element.
564	 *
565	 * @since 4.7.0
566	 *
567	 * @link https://www.php.net/manual/en/iterator.key.php
568	 *
569	 * @return mixed Returns current priority on success, or NULL on failure
570	 */
571	#[ReturnTypeWillChange]
572	public function key() {
573		return key( $this->callbacks );
574	}
575
576	/**
577	 * Checks if current position is valid.
578	 *
579	 * @since 4.7.0
580	 *
581	 * @link https://www.php.net/manual/en/iterator.valid.php
582	 *
583	 * @return bool Whether the current position is valid.
584	 */
585	#[ReturnTypeWillChange]
586	public function valid() {
587		return key( $this->callbacks ) !== null;
588	}
589
590	/**
591	 * Rewinds the Iterator to the first element.
592	 *
593	 * @since 4.7.0
594	 *
595	 * @link https://www.php.net/manual/en/iterator.rewind.php
596	 */
597	#[ReturnTypeWillChange]
598	public function rewind() {
599		reset( $this->callbacks );
600	}
601}
602