3 * The plugin API is located in this file, which allows for creating actions
4 * and filters and hooking functions, and methods. The functions or methods will
5 * then be run when the action or filter is called.
7 * The API callback examples reference functions, but can be methods of classes.
8 * To hook methods, you'll need to pass an array one of two ways.
10 * Any of the syntaxes explained in the PHP documentation for the
11 * {@link http://us2.php.net/manual/en/language.pseudo-types.php#language.types.callback 'callback'}
14 * Also see the {@link http://codex.wordpress.org/Plugin_API Plugin API} for
15 * more information and examples on how to use a lot of these functions.
23 * Hooks a function or method to a specific filter action.
25 * Filters are the hooks that WordPress launches to modify text of various types
26 * before adding it to the database or sending it to the browser screen. Plugins
27 * can specify that one or more of its PHP functions is executed to
28 * modify specific types of text at these times, using the Filter API.
30 * To use the API, the following code should be used to bind a callback to the
34 * function example_hook($example) { echo $example; }
35 * add_filter('example_filter', 'example_hook');
38 * In WordPress 1.5.1+, hooked functions can take extra arguments that are set
39 * when the matching do_action() or apply_filters() call is run. The
40 * $accepted_args allow for calling functions only when the number of args
41 * match. Hooked functions can take extra arguments that are set when the
42 * matching do_action() or apply_filters() call is run. For example, the action
43 * comment_id_not_found will pass any functions that hook onto it the ID of the
46 * <strong>Note:</strong> the function will return true no matter if the
47 * function was hooked fails or not. There are no checks for whether the
48 * function exists beforehand and no checks to whether the <tt>$function_to_add
49 * is even a string. It is up to you to take care and this is done for
50 * optimization purposes, so everything is as quick as possible.
55 * @global array $wp_filter Stores all of the filters added in the form of
56 * wp_filter['tag']['array of priorities']['array of functions serialized']['array of ['array (functions, accepted_args)']']
57 * @global array $merged_filters Tracks the tags that need to be merged for later. If the hook is added, it doesn't need to run through that process.
59 * @param string $tag The name of the filter to hook the $function_to_add to.
60 * @param callback $function_to_add The name of the function to be called when the filter is applied.
61 * @param int $priority optional. Used to specify the order in which the functions associated with a particular action are executed (default: 10). Lower numbers correspond with earlier execution, and functions with the same priority are executed in the order in which they were added to the action.
62 * @param int $accepted_args optional. The number of arguments the function accept (default 1).
63 * @return boolean true
65 function add_filter($tag, $function_to_add, $priority = 10, $accepted_args = 1) {
66 global $wp_filter, $merged_filters;
68 $idx = _wp_filter_build_unique_id($tag, $function_to_add, $priority);
69 $wp_filter[$tag][$priority][$idx] = array('function' => $function_to_add, 'accepted_args' => $accepted_args);
70 unset( $merged_filters[ $tag ] );
75 * Check if any filter has been registered for a hook.
80 * @global array $wp_filter Stores all of the filters
82 * @param string $tag The name of the filter hook.
83 * @param callback $function_to_check optional.
84 * @return mixed If $function_to_check is omitted, returns boolean for whether the hook has anything registered.
85 * When checking a specific function, the priority of that hook is returned, or false if the function is not attached.
86 * When using the $function_to_check argument, this function may return a non-boolean value that evaluates to false
87 * (e.g.) 0, so use the === operator for testing the return value.
89 function has_filter($tag, $function_to_check = false) {
92 $has = !empty($wp_filter[$tag]);
93 if ( false === $function_to_check || false == $has )
96 if ( !$idx = _wp_filter_build_unique_id($tag, $function_to_check, false) )
99 foreach ( (array) array_keys($wp_filter[$tag]) as $priority ) {
100 if ( isset($wp_filter[$tag][$priority][$idx]) )
108 * Call the functions added to a filter hook.
110 * The callback functions attached to filter hook $tag are invoked by calling
111 * this function. This function can be used to create a new filter hook by
112 * simply calling this function with the name of the new hook specified using
113 * the $tag parameter.
115 * The function allows for additional arguments to be added and passed to hooks.
117 * function example_hook($string, $arg1, $arg2)
122 * $value = apply_filters('example_filter', 'filter me', 'arg1', 'arg2');
128 * @global array $wp_filter Stores all of the filters
129 * @global array $merged_filters Merges the filter hooks using this function.
130 * @global array $wp_current_filter stores the list of current filters with the current one last
132 * @param string $tag The name of the filter hook.
133 * @param mixed $value The value on which the filters hooked to <tt>$tag</tt> are applied on.
134 * @param mixed $var,... Additional variables passed to the functions hooked to <tt>$tag</tt>.
135 * @return mixed The filtered value after all hooked functions are applied to it.
137 function apply_filters($tag, $value) {
138 global $wp_filter, $merged_filters, $wp_current_filter;
142 // Do 'all' actions first
143 if ( isset($wp_filter['all']) ) {
144 $wp_current_filter[] = $tag;
145 $args = func_get_args();
146 _wp_call_all_hook($args);
149 if ( !isset($wp_filter[$tag]) ) {
150 if ( isset($wp_filter['all']) )
151 array_pop($wp_current_filter);
155 if ( !isset($wp_filter['all']) )
156 $wp_current_filter[] = $tag;
159 if ( !isset( $merged_filters[ $tag ] ) ) {
160 ksort($wp_filter[$tag]);
161 $merged_filters[ $tag ] = true;
164 reset( $wp_filter[ $tag ] );
167 $args = func_get_args();
170 foreach( (array) current($wp_filter[$tag]) as $the_ )
171 if ( !is_null($the_['function']) ){
173 $value = call_user_func_array($the_['function'], array_slice($args, 1, (int) $the_['accepted_args']));
176 } while ( next($wp_filter[$tag]) !== false );
178 array_pop( $wp_current_filter );
184 * Execute functions hooked on a specific filter hook, specifying arguments in an array.
186 * @see apply_filters() This function is identical, but the arguments passed to the
187 * functions hooked to <tt>$tag</tt> are supplied using an array.
192 * @global array $wp_filter Stores all of the filters
193 * @global array $merged_filters Merges the filter hooks using this function.
194 * @global array $wp_current_filter stores the list of current filters with the current one last
196 * @param string $tag The name of the filter hook.
197 * @param array $args The arguments supplied to the functions hooked to <tt>$tag</tt>
198 * @return mixed The filtered value after all hooked functions are applied to it.
200 function apply_filters_ref_array($tag, $args) {
201 global $wp_filter, $merged_filters, $wp_current_filter;
203 // Do 'all' actions first
204 if ( isset($wp_filter['all']) ) {
205 $wp_current_filter[] = $tag;
206 $all_args = func_get_args();
207 _wp_call_all_hook($all_args);
210 if ( !isset($wp_filter[$tag]) ) {
211 if ( isset($wp_filter['all']) )
212 array_pop($wp_current_filter);
216 if ( !isset($wp_filter['all']) )
217 $wp_current_filter[] = $tag;
220 if ( !isset( $merged_filters[ $tag ] ) ) {
221 ksort($wp_filter[$tag]);
222 $merged_filters[ $tag ] = true;
225 reset( $wp_filter[ $tag ] );
228 foreach( (array) current($wp_filter[$tag]) as $the_ )
229 if ( !is_null($the_['function']) )
230 $args[0] = call_user_func_array($the_['function'], array_slice($args, 0, (int) $the_['accepted_args']));
232 } while ( next($wp_filter[$tag]) !== false );
234 array_pop( $wp_current_filter );
240 * Removes a function from a specified filter hook.
242 * This function removes a function attached to a specified filter hook. This
243 * method can be used to remove default functions attached to a specific filter
244 * hook and possibly replace them with a substitute.
246 * To remove a hook, the $function_to_remove and $priority arguments must match
247 * when the hook was added. This goes for both filters and actions. No warning
248 * will be given on removal failure.
254 * @param string $tag The filter hook to which the function to be removed is hooked.
255 * @param callback $function_to_remove The name of the function which should be removed.
256 * @param int $priority optional. The priority of the function (default: 10).
257 * @param int $accepted_args optional. The number of arguments the function accepts (default: 1).
258 * @return boolean Whether the function existed before it was removed.
260 function remove_filter( $tag, $function_to_remove, $priority = 10 ) {
261 $function_to_remove = _wp_filter_build_unique_id($tag, $function_to_remove, $priority);
263 $r = isset($GLOBALS['wp_filter'][$tag][$priority][$function_to_remove]);
266 unset($GLOBALS['wp_filter'][$tag][$priority][$function_to_remove]);
267 if ( empty($GLOBALS['wp_filter'][$tag][$priority]) )
268 unset($GLOBALS['wp_filter'][$tag][$priority]);
269 unset($GLOBALS['merged_filters'][$tag]);
276 * Remove all of the hooks from a filter.
280 * @param string $tag The filter to remove hooks from.
281 * @param int $priority The priority number to remove.
282 * @return bool True when finished.
284 function remove_all_filters($tag, $priority = false) {
285 global $wp_filter, $merged_filters;
287 if( isset($wp_filter[$tag]) ) {
288 if( false !== $priority && isset($wp_filter[$tag][$priority]) )
289 unset($wp_filter[$tag][$priority]);
291 unset($wp_filter[$tag]);
294 if( isset($merged_filters[$tag]) )
295 unset($merged_filters[$tag]);
301 * Retrieve the name of the current filter or action.
307 * @return string Hook name of the current filter or action.
309 function current_filter() {
310 global $wp_current_filter;
311 return end( $wp_current_filter );
315 * Hooks a function on to a specific action.
317 * Actions are the hooks that the WordPress core launches at specific points
318 * during execution, or when specific events occur. Plugins can specify that
319 * one or more of its PHP functions are executed at these points, using the
322 * @uses add_filter() Adds an action. Parameter list and functionality are the same.
328 * @param string $tag The name of the action to which the $function_to_add is hooked.
329 * @param callback $function_to_add The name of the function you wish to be called.
330 * @param int $priority optional. Used to specify the order in which the functions associated with a particular action are executed (default: 10). Lower numbers correspond with earlier execution, and functions with the same priority are executed in the order in which they were added to the action.
331 * @param int $accepted_args optional. The number of arguments the function accept (default 1).
333 function add_action($tag, $function_to_add, $priority = 10, $accepted_args = 1) {
334 return add_filter($tag, $function_to_add, $priority, $accepted_args);
338 * Execute functions hooked on a specific action hook.
340 * This function invokes all functions attached to action hook $tag. It is
341 * possible to create new action hooks by simply calling this function,
342 * specifying the name of the new hook using the <tt>$tag</tt> parameter.
344 * You can pass extra arguments to the hooks, much like you can with
347 * @see apply_filters() This function works similar with the exception that
348 * nothing is returned and only the functions or methods are called.
353 * @global array $wp_filter Stores all of the filters
354 * @global array $wp_actions Increments the amount of times action was triggered.
356 * @param string $tag The name of the action to be executed.
357 * @param mixed $arg,... Optional additional arguments which are passed on to the functions hooked to the action.
358 * @return null Will return null if $tag does not exist in $wp_filter array
360 function do_action($tag, $arg = '') {
361 global $wp_filter, $wp_actions, $merged_filters, $wp_current_filter;
363 if ( ! isset($wp_actions) )
364 $wp_actions = array();
366 if ( ! isset($wp_actions[$tag]) )
367 $wp_actions[$tag] = 1;
371 // Do 'all' actions first
372 if ( isset($wp_filter['all']) ) {
373 $wp_current_filter[] = $tag;
374 $all_args = func_get_args();
375 _wp_call_all_hook($all_args);
378 if ( !isset($wp_filter[$tag]) ) {
379 if ( isset($wp_filter['all']) )
380 array_pop($wp_current_filter);
384 if ( !isset($wp_filter['all']) )
385 $wp_current_filter[] = $tag;
388 if ( is_array($arg) && 1 == count($arg) && isset($arg[0]) && is_object($arg[0]) ) // array(&$this)
392 for ( $a = 2; $a < func_num_args(); $a++ )
393 $args[] = func_get_arg($a);
396 if ( !isset( $merged_filters[ $tag ] ) ) {
397 ksort($wp_filter[$tag]);
398 $merged_filters[ $tag ] = true;
401 reset( $wp_filter[ $tag ] );
404 foreach ( (array) current($wp_filter[$tag]) as $the_ )
405 if ( !is_null($the_['function']) )
406 call_user_func_array($the_['function'], array_slice($args, 0, (int) $the_['accepted_args']));
408 } while ( next($wp_filter[$tag]) !== false );
410 array_pop($wp_current_filter);
414 * Retrieve the number of times an action is fired.
419 * @global array $wp_actions Increments the amount of times action was triggered.
421 * @param string $tag The name of the action hook.
422 * @return int The number of times action hook <tt>$tag</tt> is fired
424 function did_action($tag) {
427 if ( ! isset( $wp_actions ) || ! isset( $wp_actions[$tag] ) )
430 return $wp_actions[$tag];
434 * Execute functions hooked on a specific action hook, specifying arguments in an array.
436 * @see do_action() This function is identical, but the arguments passed to the
437 * functions hooked to <tt>$tag</tt> are supplied using an array.
442 * @global array $wp_filter Stores all of the filters
443 * @global array $wp_actions Increments the amount of times action was triggered.
445 * @param string $tag The name of the action to be executed.
446 * @param array $args The arguments supplied to the functions hooked to <tt>$tag</tt>
447 * @return null Will return null if $tag does not exist in $wp_filter array
449 function do_action_ref_array($tag, $args) {
450 global $wp_filter, $wp_actions, $merged_filters, $wp_current_filter;
452 if ( ! isset($wp_actions) )
453 $wp_actions = array();
455 if ( ! isset($wp_actions[$tag]) )
456 $wp_actions[$tag] = 1;
460 // Do 'all' actions first
461 if ( isset($wp_filter['all']) ) {
462 $wp_current_filter[] = $tag;
463 $all_args = func_get_args();
464 _wp_call_all_hook($all_args);
467 if ( !isset($wp_filter[$tag]) ) {
468 if ( isset($wp_filter['all']) )
469 array_pop($wp_current_filter);
473 if ( !isset($wp_filter['all']) )
474 $wp_current_filter[] = $tag;
477 if ( !isset( $merged_filters[ $tag ] ) ) {
478 ksort($wp_filter[$tag]);
479 $merged_filters[ $tag ] = true;
482 reset( $wp_filter[ $tag ] );
485 foreach( (array) current($wp_filter[$tag]) as $the_ )
486 if ( !is_null($the_['function']) )
487 call_user_func_array($the_['function'], array_slice($args, 0, (int) $the_['accepted_args']));
489 } while ( next($wp_filter[$tag]) !== false );
491 array_pop($wp_current_filter);
495 * Check if any action has been registered for a hook.
500 * @see has_filter() has_action() is an alias of has_filter().
502 * @param string $tag The name of the action hook.
503 * @param callback $function_to_check optional.
504 * @return mixed If $function_to_check is omitted, returns boolean for whether the hook has anything registered.
505 * When checking a specific function, the priority of that hook is returned, or false if the function is not attached.
506 * When using the $function_to_check argument, this function may return a non-boolean value that evaluates to false
507 * (e.g.) 0, so use the === operator for testing the return value.
509 function has_action($tag, $function_to_check = false) {
510 return has_filter($tag, $function_to_check);
514 * Removes a function from a specified action hook.
516 * This function removes a function attached to a specified action hook. This
517 * method can be used to remove default functions attached to a specific filter
518 * hook and possibly replace them with a substitute.
524 * @param string $tag The action hook to which the function to be removed is hooked.
525 * @param callback $function_to_remove The name of the function which should be removed.
526 * @param int $priority optional The priority of the function (default: 10).
527 * @return boolean Whether the function is removed.
529 function remove_action( $tag, $function_to_remove, $priority = 10 ) {
530 return remove_filter( $tag, $function_to_remove, $priority );
534 * Remove all of the hooks from an action.
538 * @param string $tag The action to remove hooks from.
539 * @param int $priority The priority number to remove them from.
540 * @return bool True when finished.
542 function remove_all_actions($tag, $priority = false) {
543 return remove_all_filters($tag, $priority);
547 // Functions for handling plugins.
551 * Gets the basename of a plugin.
553 * This method extracts the name of a plugin from its filename.
561 * @param string $file The filename of plugin.
562 * @return string The name of a plugin.
563 * @uses WP_PLUGIN_DIR
565 function plugin_basename($file) {
566 $file = str_replace('\\','/',$file); // sanitize for Win32 installs
567 $file = preg_replace('|/+|','/', $file); // remove any duplicate slash
568 $plugin_dir = str_replace('\\','/',WP_PLUGIN_DIR); // sanitize for Win32 installs
569 $plugin_dir = preg_replace('|/+|','/', $plugin_dir); // remove any duplicate slash
570 $mu_plugin_dir = str_replace('\\','/',WPMU_PLUGIN_DIR); // sanitize for Win32 installs
571 $mu_plugin_dir = preg_replace('|/+|','/', $mu_plugin_dir); // remove any duplicate slash
572 $file = preg_replace('#^' . preg_quote($plugin_dir, '#') . '/|^' . preg_quote($mu_plugin_dir, '#') . '/#','',$file); // get relative path from plugins dir
573 $file = trim($file, '/');
578 * Gets the filesystem directory path (with trailing slash) for the plugin __FILE__ passed in
583 * @param string $file The filename of the plugin (__FILE__)
584 * @return string the filesystem path of the directory that contains the plugin
586 function plugin_dir_path( $file ) {
587 return trailingslashit( dirname( $file ) );
591 * Gets the URL directory path (with trailing slash) for the plugin __FILE__ passed in
596 * @param string $file The filename of the plugin (__FILE__)
597 * @return string the URL path of the directory that contains the plugin
599 function plugin_dir_url( $file ) {
600 return trailingslashit( plugins_url( '', $file ) );
604 * Set the activation hook for a plugin.
606 * When a plugin is activated, the action 'activate_PLUGINNAME' hook is
607 * activated. In the name of this hook, PLUGINNAME is replaced with the name of
608 * the plugin, including the optional subdirectory. For example, when the plugin
609 * is located in wp-content/plugin/sampleplugin/sample.php, then the name of
610 * this hook will become 'activate_sampleplugin/sample.php'. When the plugin
611 * consists of only one file and is (as by default) located at
612 * wp-content/plugin/sample.php the name of this hook will be
613 * 'activate_sample.php'.
619 * @param string $file The filename of the plugin including the path.
620 * @param callback $function the function hooked to the 'activate_PLUGIN' action.
622 function register_activation_hook($file, $function) {
623 $file = plugin_basename($file);
624 add_action('activate_' . $file, $function);
628 * Set the deactivation hook for a plugin.
630 * When a plugin is deactivated, the action 'deactivate_PLUGINNAME' hook is
631 * deactivated. In the name of this hook, PLUGINNAME is replaced with the name
632 * of the plugin, including the optional subdirectory. For example, when the
633 * plugin is located in wp-content/plugin/sampleplugin/sample.php, then
634 * the name of this hook will become 'activate_sampleplugin/sample.php'.
636 * When the plugin consists of only one file and is (as by default) located at
637 * wp-content/plugin/sample.php the name of this hook will be
638 * 'activate_sample.php'.
644 * @param string $file The filename of the plugin including the path.
645 * @param callback $function the function hooked to the 'activate_PLUGIN' action.
647 function register_deactivation_hook($file, $function) {
648 $file = plugin_basename($file);
649 add_action('deactivate_' . $file, $function);
653 * Set the uninstallation hook for a plugin.
655 * Registers the uninstall hook that will be called when the user clicks on the
656 * uninstall link that calls for the plugin to uninstall itself. The link won't
657 * be active unless the plugin hooks into the action.
659 * The plugin should not run arbitrary code outside of functions, when
660 * registering the uninstall hook. In order to run using the hook, the plugin
661 * will have to be included, which means that any code laying outside of a
662 * function will be run during the uninstall process. The plugin should not
663 * hinder the uninstall process.
665 * If the plugin can not be written without running code within the plugin, then
666 * the plugin should create a file named 'uninstall.php' in the base plugin
667 * folder. This file will be called, if it exists, during the uninstall process
668 * bypassing the uninstall hook. The plugin, when using the 'uninstall.php'
669 * should always check for the 'WP_UNINSTALL_PLUGIN' constant, before
674 * @param string $file
675 * @param callback $callback The callback to run when the hook is called. Must be a static method or function.
677 function register_uninstall_hook( $file, $callback ) {
678 if ( is_array( $callback ) && is_object( $callback[0] ) ) {
679 _doing_it_wrong( __FUNCTION__, __( 'Only a static class method or function can be used in an uninstall hook.' ), '3.1' );
683 // The option should not be autoloaded, because it is not needed in most
684 // cases. Emphasis should be put on using the 'uninstall.php' way of
685 // uninstalling the plugin.
686 $uninstallable_plugins = (array) get_option('uninstall_plugins');
687 $uninstallable_plugins[plugin_basename($file)] = $callback;
688 update_option('uninstall_plugins', $uninstallable_plugins);
692 * Calls the 'all' hook, which will process the functions hooked into it.
694 * The 'all' hook passes all of the arguments or parameters that were used for
695 * the hook, which this function was called for.
697 * This function is used internally for apply_filters(), do_action(), and
698 * do_action_ref_array() and is not meant to be used from outside those
699 * functions. This function does not check for the existence of the all hook, so
700 * it will fail unless the all hook exists prior to this function call.
707 * @uses $wp_filter Used to process all of the functions in the 'all' hook
709 * @param array $args The collected parameters from the hook that was called.
710 * @param string $hook Optional. The hook name that was used to call the 'all' hook.
712 function _wp_call_all_hook($args) {
715 reset( $wp_filter['all'] );
717 foreach( (array) current($wp_filter['all']) as $the_ )
718 if ( !is_null($the_['function']) )
719 call_user_func_array($the_['function'], $args);
721 } while ( next($wp_filter['all']) !== false );
725 * Build Unique ID for storage and retrieval.
727 * The old way to serialize the callback caused issues and this function is the
728 * solution. It works by checking for objects and creating an a new property in
729 * the class to keep track of the object and new objects of the same class that
732 * It also allows for the removal of actions and filters for objects after they
733 * change class properties. It is possible to include the property $wp_filter_id
734 * in your class and set it to "null" or a number to bypass the workaround.
735 * However this will prevent you from adding new classes and any new classes
736 * will overwrite the previous hook by the same class.
738 * Functions and static method callbacks are just returned as strings and
739 * shouldn't have any speed penalty.
745 * @link http://trac.wordpress.org/ticket/3875
747 * @global array $wp_filter Storage for all of the filters and actions
748 * @param string $tag Used in counting how many hooks were applied
749 * @param callback $function Used for creating unique id
750 * @param int|bool $priority Used in counting how many hooks were applied. If === false and $function is an object reference, we return the unique id only if it already has one, false otherwise.
751 * @return string|bool Unique ID for usage as array key or false if $priority === false and $function is an object reference, and it does not already have a unique id.
753 function _wp_filter_build_unique_id($tag, $function, $priority) {
755 static $filter_id_count = 0;
757 if ( is_string($function) )
760 if ( is_object($function) ) {
761 // Closures are currently implemented as objects
762 $function = array( $function, '' );
764 $function = (array) $function;
767 if (is_object($function[0]) ) {
768 // Object Class Calling
769 if ( function_exists('spl_object_hash') ) {
770 return spl_object_hash($function[0]) . $function[1];
772 $obj_idx = get_class($function[0]).$function[1];
773 if ( !isset($function[0]->wp_filter_id) ) {
774 if ( false === $priority )
776 $obj_idx .= isset($wp_filter[$tag][$priority]) ? count((array)$wp_filter[$tag][$priority]) : $filter_id_count;
777 $function[0]->wp_filter_id = $filter_id_count;
780 $obj_idx .= $function[0]->wp_filter_id;
785 } else if ( is_string($function[0]) ) {
787 return $function[0].$function[1];