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.
22 // Initialize the filter globals.
23 global $wp_filter, $wp_actions, $merged_filters, $wp_current_filter;
25 if ( ! isset( $wp_filter ) )
28 if ( ! isset( $wp_actions ) )
29 $wp_actions = array();
31 if ( ! isset( $merged_filters ) )
32 $merged_filters = array();
34 if ( ! isset( $wp_current_filter ) )
35 $wp_current_filter = array();
38 * Hooks a function or method to a specific filter action.
40 * WordPress offers filter hooks to allow plugins to modify
41 * various types of internal data at runtime.
43 * A plugin can modify data by binding a callback to a filter hook. When the filter
44 * is later applied, each bound callback is run in order of priority, and given
45 * the opportunity to modify a value by returning a new value.
47 * The following example shows how a callback function is bound to a filter hook.
48 * Note that $example is passed to the callback, (maybe) modified, then returned:
51 * function example_callback( $example ) {
52 * // Maybe modify $example in some way
55 * add_filter( 'example_filter', 'example_callback' );
58 * Since WordPress 1.5.1, bound callbacks can take as many arguments as are
59 * passed as parameters in the corresponding apply_filters() call. The $accepted_args
60 * parameter allows for calling functions only when the number of args match.
62 * <strong>Note:</strong> the function will return true whether or not the callback
63 * is valid. It is up to you to take care. This is done for optimization purposes,
64 * so everything is as quick as possible.
69 * @global array $wp_filter A multidimensional array of all hooks and the callbacks hooked to them.
70 * @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.
74 * @param string $tag The name of the filter to hook the $function_to_add callback to.
75 * @param callback $function_to_add The callback to be run when the filter is applied.
76 * @param int $priority (optional) The order in which the functions associated with a particular action are executed. 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.
78 * @param int $accepted_args (optional) The number of arguments the function accepts.
80 * @return boolean true
82 function add_filter( $tag, $function_to_add, $priority = 10, $accepted_args = 1 ) {
83 global $wp_filter, $merged_filters;
85 $idx = _wp_filter_build_unique_id($tag, $function_to_add, $priority);
86 $wp_filter[$tag][$priority][$idx] = array('function' => $function_to_add, 'accepted_args' => $accepted_args);
87 unset( $merged_filters[ $tag ] );
92 * Check if any filter has been registered for a hook.
97 * @global array $wp_filter Stores all of the filters
99 * @param string $tag The name of the filter hook.
100 * @param callback $function_to_check optional.
101 * @return mixed If $function_to_check is omitted, returns boolean for whether the hook has anything registered.
102 * When checking a specific function, the priority of that hook is returned, or false if the function is not attached.
103 * When using the $function_to_check argument, this function may return a non-boolean value that evaluates to false
104 * (e.g.) 0, so use the === operator for testing the return value.
106 function has_filter($tag, $function_to_check = false) {
109 $has = !empty($wp_filter[$tag]);
110 if ( false === $function_to_check || false == $has )
113 if ( !$idx = _wp_filter_build_unique_id($tag, $function_to_check, false) )
116 foreach ( (array) array_keys($wp_filter[$tag]) as $priority ) {
117 if ( isset($wp_filter[$tag][$priority][$idx]) )
125 * Call the functions added to a filter hook.
127 * The callback functions attached to filter hook $tag are invoked by calling
128 * this function. This function can be used to create a new filter hook by
129 * simply calling this function with the name of the new hook specified using
130 * the $tag parameter.
132 * The function allows for additional arguments to be added and passed to hooks.
134 * // Our filter callback function
135 * function example_callback( $string, $arg1, $arg2 ) {
136 * // (maybe) modify $string
139 * add_filter( 'example_filter', 'example_callback', 10, 3 );
141 * // Apply the filters by calling the 'example_callback' function we
142 * // "hooked" to 'example_filter' using the add_filter() function above.
143 * // - 'example_filter' is the filter hook $tag
144 * // - 'filter me' is the value being filtered
145 * // - $arg1 and $arg2 are the additional arguments passed to the callback.
146 * $value = apply_filters( 'example_filter', 'filter me', $arg1, $arg2 );
152 * @global array $wp_filter Stores all of the filters
153 * @global array $merged_filters Merges the filter hooks using this function.
154 * @global array $wp_current_filter stores the list of current filters with the current one last
158 * @param string $tag The name of the filter hook.
159 * @param mixed $value The value on which the filters hooked to <tt>$tag</tt> are applied on.
160 * @param mixed $var Additional variables passed to the functions hooked to <tt>$tag</tt>.
161 * @return mixed The filtered value after all hooked functions are applied to it.
163 function apply_filters( $tag, $value ) {
164 global $wp_filter, $merged_filters, $wp_current_filter;
168 // Do 'all' actions first
169 if ( isset($wp_filter['all']) ) {
170 $wp_current_filter[] = $tag;
171 $args = func_get_args();
172 _wp_call_all_hook($args);
175 if ( !isset($wp_filter[$tag]) ) {
176 if ( isset($wp_filter['all']) )
177 array_pop($wp_current_filter);
181 if ( !isset($wp_filter['all']) )
182 $wp_current_filter[] = $tag;
185 if ( !isset( $merged_filters[ $tag ] ) ) {
186 ksort($wp_filter[$tag]);
187 $merged_filters[ $tag ] = true;
190 reset( $wp_filter[ $tag ] );
193 $args = func_get_args();
196 foreach( (array) current($wp_filter[$tag]) as $the_ )
197 if ( !is_null($the_['function']) ){
199 $value = call_user_func_array($the_['function'], array_slice($args, 1, (int) $the_['accepted_args']));
202 } while ( next($wp_filter[$tag]) !== false );
204 array_pop( $wp_current_filter );
210 * Execute functions hooked on a specific filter hook, specifying arguments in an array.
212 * @see apply_filters() This function is identical, but the arguments passed to the
213 * functions hooked to <tt>$tag</tt> are supplied using an array.
218 * @global array $wp_filter Stores all of the filters
219 * @global array $merged_filters Merges the filter hooks using this function.
220 * @global array $wp_current_filter stores the list of current filters with the current one last
222 * @param string $tag The name of the filter hook.
223 * @param array $args The arguments supplied to the functions hooked to <tt>$tag</tt>
224 * @return mixed The filtered value after all hooked functions are applied to it.
226 function apply_filters_ref_array($tag, $args) {
227 global $wp_filter, $merged_filters, $wp_current_filter;
229 // Do 'all' actions first
230 if ( isset($wp_filter['all']) ) {
231 $wp_current_filter[] = $tag;
232 $all_args = func_get_args();
233 _wp_call_all_hook($all_args);
236 if ( !isset($wp_filter[$tag]) ) {
237 if ( isset($wp_filter['all']) )
238 array_pop($wp_current_filter);
242 if ( !isset($wp_filter['all']) )
243 $wp_current_filter[] = $tag;
246 if ( !isset( $merged_filters[ $tag ] ) ) {
247 ksort($wp_filter[$tag]);
248 $merged_filters[ $tag ] = true;
251 reset( $wp_filter[ $tag ] );
254 foreach( (array) current($wp_filter[$tag]) as $the_ )
255 if ( !is_null($the_['function']) )
256 $args[0] = call_user_func_array($the_['function'], array_slice($args, 0, (int) $the_['accepted_args']));
258 } while ( next($wp_filter[$tag]) !== false );
260 array_pop( $wp_current_filter );
266 * Removes a function from a specified filter hook.
268 * This function removes a function attached to a specified filter hook. This
269 * method can be used to remove default functions attached to a specific filter
270 * hook and possibly replace them with a substitute.
272 * To remove a hook, the $function_to_remove and $priority arguments must match
273 * when the hook was added. This goes for both filters and actions. No warning
274 * will be given on removal failure.
280 * @param string $tag The filter hook to which the function to be removed is hooked.
281 * @param callback $function_to_remove The name of the function which should be removed.
282 * @param int $priority optional. The priority of the function (default: 10).
283 * @param int $accepted_args optional. The number of arguments the function accepts (default: 1).
284 * @return boolean Whether the function existed before it was removed.
286 function remove_filter( $tag, $function_to_remove, $priority = 10 ) {
287 $function_to_remove = _wp_filter_build_unique_id($tag, $function_to_remove, $priority);
289 $r = isset($GLOBALS['wp_filter'][$tag][$priority][$function_to_remove]);
292 unset($GLOBALS['wp_filter'][$tag][$priority][$function_to_remove]);
293 if ( empty($GLOBALS['wp_filter'][$tag][$priority]) )
294 unset($GLOBALS['wp_filter'][$tag][$priority]);
295 unset($GLOBALS['merged_filters'][$tag]);
302 * Remove all of the hooks from a filter.
306 * @param string $tag The filter to remove hooks from.
307 * @param int $priority The priority number to remove.
308 * @return bool True when finished.
310 function remove_all_filters($tag, $priority = false) {
311 global $wp_filter, $merged_filters;
313 if( isset($wp_filter[$tag]) ) {
314 if( false !== $priority && isset($wp_filter[$tag][$priority]) )
315 unset($wp_filter[$tag][$priority]);
317 unset($wp_filter[$tag]);
320 if( isset($merged_filters[$tag]) )
321 unset($merged_filters[$tag]);
327 * Retrieve the name of the current filter or action.
333 * @return string Hook name of the current filter or action.
335 function current_filter() {
336 global $wp_current_filter;
337 return end( $wp_current_filter );
341 * Hooks a function on to a specific action.
343 * Actions are the hooks that the WordPress core launches at specific points
344 * during execution, or when specific events occur. Plugins can specify that
345 * one or more of its PHP functions are executed at these points, using the
348 * @uses add_filter() Adds an action. Parameter list and functionality are the same.
354 * @param string $tag The name of the action to which the $function_to_add is hooked.
355 * @param callback $function_to_add The name of the function you wish to be called.
356 * @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.
357 * @param int $accepted_args optional. The number of arguments the function accept (default 1).
359 function add_action($tag, $function_to_add, $priority = 10, $accepted_args = 1) {
360 return add_filter($tag, $function_to_add, $priority, $accepted_args);
364 * Execute functions hooked on a specific action hook.
366 * This function invokes all functions attached to action hook $tag. It is
367 * possible to create new action hooks by simply calling this function,
368 * specifying the name of the new hook using the <tt>$tag</tt> parameter.
370 * You can pass extra arguments to the hooks, much like you can with
373 * @see apply_filters() This function works similar with the exception that
374 * nothing is returned and only the functions or methods are called.
379 * @global array $wp_filter Stores all of the filters
380 * @global array $wp_actions Increments the amount of times action was triggered.
382 * @param string $tag The name of the action to be executed.
383 * @param mixed $arg,... Optional additional arguments which are passed on to the functions hooked to the action.
384 * @return null Will return null if $tag does not exist in $wp_filter array
386 function do_action($tag, $arg = '') {
387 global $wp_filter, $wp_actions, $merged_filters, $wp_current_filter;
389 if ( ! isset($wp_actions[$tag]) )
390 $wp_actions[$tag] = 1;
394 // Do 'all' actions first
395 if ( isset($wp_filter['all']) ) {
396 $wp_current_filter[] = $tag;
397 $all_args = func_get_args();
398 _wp_call_all_hook($all_args);
401 if ( !isset($wp_filter[$tag]) ) {
402 if ( isset($wp_filter['all']) )
403 array_pop($wp_current_filter);
407 if ( !isset($wp_filter['all']) )
408 $wp_current_filter[] = $tag;
411 if ( is_array($arg) && 1 == count($arg) && isset($arg[0]) && is_object($arg[0]) ) // array(&$this)
415 for ( $a = 2; $a < func_num_args(); $a++ )
416 $args[] = func_get_arg($a);
419 if ( !isset( $merged_filters[ $tag ] ) ) {
420 ksort($wp_filter[$tag]);
421 $merged_filters[ $tag ] = true;
424 reset( $wp_filter[ $tag ] );
427 foreach ( (array) current($wp_filter[$tag]) as $the_ )
428 if ( !is_null($the_['function']) )
429 call_user_func_array($the_['function'], array_slice($args, 0, (int) $the_['accepted_args']));
431 } while ( next($wp_filter[$tag]) !== false );
433 array_pop($wp_current_filter);
437 * Retrieve the number of times an action is fired.
442 * @global array $wp_actions Increments the amount of times action was triggered.
444 * @param string $tag The name of the action hook.
445 * @return int The number of times action hook <tt>$tag</tt> is fired
447 function did_action($tag) {
450 if ( ! isset( $wp_actions[ $tag ] ) )
453 return $wp_actions[$tag];
457 * Execute functions hooked on a specific action hook, specifying arguments in an array.
459 * @see do_action() This function is identical, but the arguments passed to the
460 * functions hooked to <tt>$tag</tt> are supplied using an array.
465 * @global array $wp_filter Stores all of the filters
466 * @global array $wp_actions Increments the amount of times action was triggered.
468 * @param string $tag The name of the action to be executed.
469 * @param array $args The arguments supplied to the functions hooked to <tt>$tag</tt>
470 * @return null Will return null if $tag does not exist in $wp_filter array
472 function do_action_ref_array($tag, $args) {
473 global $wp_filter, $wp_actions, $merged_filters, $wp_current_filter;
475 if ( ! isset($wp_actions[$tag]) )
476 $wp_actions[$tag] = 1;
480 // Do 'all' actions first
481 if ( isset($wp_filter['all']) ) {
482 $wp_current_filter[] = $tag;
483 $all_args = func_get_args();
484 _wp_call_all_hook($all_args);
487 if ( !isset($wp_filter[$tag]) ) {
488 if ( isset($wp_filter['all']) )
489 array_pop($wp_current_filter);
493 if ( !isset($wp_filter['all']) )
494 $wp_current_filter[] = $tag;
497 if ( !isset( $merged_filters[ $tag ] ) ) {
498 ksort($wp_filter[$tag]);
499 $merged_filters[ $tag ] = true;
502 reset( $wp_filter[ $tag ] );
505 foreach( (array) current($wp_filter[$tag]) as $the_ )
506 if ( !is_null($the_['function']) )
507 call_user_func_array($the_['function'], array_slice($args, 0, (int) $the_['accepted_args']));
509 } while ( next($wp_filter[$tag]) !== false );
511 array_pop($wp_current_filter);
515 * Check if any action has been registered for a hook.
520 * @see has_filter() has_action() is an alias of has_filter().
522 * @param string $tag The name of the action hook.
523 * @param callback $function_to_check optional.
524 * @return mixed If $function_to_check is omitted, returns boolean for whether the hook has anything registered.
525 * When checking a specific function, the priority of that hook is returned, or false if the function is not attached.
526 * When using the $function_to_check argument, this function may return a non-boolean value that evaluates to false
527 * (e.g.) 0, so use the === operator for testing the return value.
529 function has_action($tag, $function_to_check = false) {
530 return has_filter($tag, $function_to_check);
534 * Removes a function from a specified action hook.
536 * This function removes a function attached to a specified action hook. This
537 * method can be used to remove default functions attached to a specific filter
538 * hook and possibly replace them with a substitute.
544 * @param string $tag The action hook to which the function to be removed is hooked.
545 * @param callback $function_to_remove The name of the function which should be removed.
546 * @param int $priority optional The priority of the function (default: 10).
547 * @return boolean Whether the function is removed.
549 function remove_action( $tag, $function_to_remove, $priority = 10 ) {
550 return remove_filter( $tag, $function_to_remove, $priority );
554 * Remove all of the hooks from an action.
558 * @param string $tag The action to remove hooks from.
559 * @param int $priority The priority number to remove them from.
560 * @return bool True when finished.
562 function remove_all_actions($tag, $priority = false) {
563 return remove_all_filters($tag, $priority);
567 // Functions for handling plugins.
571 * Gets the basename of a plugin.
573 * This method extracts the name of a plugin from its filename.
581 * @param string $file The filename of plugin.
582 * @return string The name of a plugin.
583 * @uses WP_PLUGIN_DIR
585 function plugin_basename($file) {
586 $file = str_replace('\\','/',$file); // sanitize for Win32 installs
587 $file = preg_replace('|/+|','/', $file); // remove any duplicate slash
588 $plugin_dir = str_replace('\\','/',WP_PLUGIN_DIR); // sanitize for Win32 installs
589 $plugin_dir = preg_replace('|/+|','/', $plugin_dir); // remove any duplicate slash
590 $mu_plugin_dir = str_replace('\\','/',WPMU_PLUGIN_DIR); // sanitize for Win32 installs
591 $mu_plugin_dir = preg_replace('|/+|','/', $mu_plugin_dir); // remove any duplicate slash
592 $file = preg_replace('#^' . preg_quote($plugin_dir, '#') . '/|^' . preg_quote($mu_plugin_dir, '#') . '/#','',$file); // get relative path from plugins dir
593 $file = trim($file, '/');
598 * Gets the filesystem directory path (with trailing slash) for the plugin __FILE__ passed in
603 * @param string $file The filename of the plugin (__FILE__)
604 * @return string the filesystem path of the directory that contains the plugin
606 function plugin_dir_path( $file ) {
607 return trailingslashit( dirname( $file ) );
611 * Gets the URL directory path (with trailing slash) for the plugin __FILE__ passed in
616 * @param string $file The filename of the plugin (__FILE__)
617 * @return string the URL path of the directory that contains the plugin
619 function plugin_dir_url( $file ) {
620 return trailingslashit( plugins_url( '', $file ) );
624 * Set the activation hook for a plugin.
626 * When a plugin is activated, the action 'activate_PLUGINNAME' hook is
627 * called. In the name of this hook, PLUGINNAME is replaced with the name
628 * of the plugin, including the optional subdirectory. For example, when the
629 * plugin is located in wp-content/plugins/sampleplugin/sample.php, then
630 * the name of this hook will become 'activate_sampleplugin/sample.php'.
632 * When the plugin consists of only one file and is (as by default) located at
633 * wp-content/plugins/sample.php the name of this hook will be
634 * 'activate_sample.php'.
640 * @param string $file The filename of the plugin including the path.
641 * @param callback $function the function hooked to the 'activate_PLUGIN' action.
643 function register_activation_hook($file, $function) {
644 $file = plugin_basename($file);
645 add_action('activate_' . $file, $function);
649 * Set the deactivation hook for a plugin.
651 * When a plugin is deactivated, the action 'deactivate_PLUGINNAME' hook is
652 * called. In the name of this hook, PLUGINNAME is replaced with the name
653 * of the plugin, including the optional subdirectory. For example, when the
654 * plugin is located in wp-content/plugins/sampleplugin/sample.php, then
655 * the name of this hook will become 'deactivate_sampleplugin/sample.php'.
657 * When the plugin consists of only one file and is (as by default) located at
658 * wp-content/plugins/sample.php the name of this hook will be
659 * 'deactivate_sample.php'.
665 * @param string $file The filename of the plugin including the path.
666 * @param callback $function the function hooked to the 'deactivate_PLUGIN' action.
668 function register_deactivation_hook($file, $function) {
669 $file = plugin_basename($file);
670 add_action('deactivate_' . $file, $function);
674 * Set the uninstallation hook for a plugin.
676 * Registers the uninstall hook that will be called when the user clicks on the
677 * uninstall link that calls for the plugin to uninstall itself. The link won't
678 * be active unless the plugin hooks into the action.
680 * The plugin should not run arbitrary code outside of functions, when
681 * registering the uninstall hook. In order to run using the hook, the plugin
682 * will have to be included, which means that any code laying outside of a
683 * function will be run during the uninstall process. The plugin should not
684 * hinder the uninstall process.
686 * If the plugin can not be written without running code within the plugin, then
687 * the plugin should create a file named 'uninstall.php' in the base plugin
688 * folder. This file will be called, if it exists, during the uninstall process
689 * bypassing the uninstall hook. The plugin, when using the 'uninstall.php'
690 * should always check for the 'WP_UNINSTALL_PLUGIN' constant, before
695 * @param string $file
696 * @param callback $callback The callback to run when the hook is called. Must be a static method or function.
698 function register_uninstall_hook( $file, $callback ) {
699 if ( is_array( $callback ) && is_object( $callback[0] ) ) {
700 _doing_it_wrong( __FUNCTION__, __( 'Only a static class method or function can be used in an uninstall hook.' ), '3.1' );
704 // The option should not be autoloaded, because it is not needed in most
705 // cases. Emphasis should be put on using the 'uninstall.php' way of
706 // uninstalling the plugin.
707 $uninstallable_plugins = (array) get_option('uninstall_plugins');
708 $uninstallable_plugins[plugin_basename($file)] = $callback;
709 update_option('uninstall_plugins', $uninstallable_plugins);
713 * Calls the 'all' hook, which will process the functions hooked into it.
715 * The 'all' hook passes all of the arguments or parameters that were used for
716 * the hook, which this function was called for.
718 * This function is used internally for apply_filters(), do_action(), and
719 * do_action_ref_array() and is not meant to be used from outside those
720 * functions. This function does not check for the existence of the all hook, so
721 * it will fail unless the all hook exists prior to this function call.
728 * @uses $wp_filter Used to process all of the functions in the 'all' hook
730 * @param array $args The collected parameters from the hook that was called.
732 function _wp_call_all_hook($args) {
735 reset( $wp_filter['all'] );
737 foreach( (array) current($wp_filter['all']) as $the_ )
738 if ( !is_null($the_['function']) )
739 call_user_func_array($the_['function'], $args);
741 } while ( next($wp_filter['all']) !== false );
745 * Build Unique ID for storage and retrieval.
747 * The old way to serialize the callback caused issues and this function is the
748 * solution. It works by checking for objects and creating an a new property in
749 * the class to keep track of the object and new objects of the same class that
752 * It also allows for the removal of actions and filters for objects after they
753 * change class properties. It is possible to include the property $wp_filter_id
754 * in your class and set it to "null" or a number to bypass the workaround.
755 * However this will prevent you from adding new classes and any new classes
756 * will overwrite the previous hook by the same class.
758 * Functions and static method callbacks are just returned as strings and
759 * shouldn't have any speed penalty.
765 * @link http://trac.wordpress.org/ticket/3875
767 * @global array $wp_filter Storage for all of the filters and actions
768 * @param string $tag Used in counting how many hooks were applied
769 * @param callback $function Used for creating unique id
770 * @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.
771 * @return string|bool Unique ID for usage as array key or false if $priority === false and $function is an object reference, and it does not already have a unique id.
773 function _wp_filter_build_unique_id($tag, $function, $priority) {
775 static $filter_id_count = 0;
777 if ( is_string($function) )
780 if ( is_object($function) ) {
781 // Closures are currently implemented as objects
782 $function = array( $function, '' );
784 $function = (array) $function;
787 if (is_object($function[0]) ) {
788 // Object Class Calling
789 if ( function_exists('spl_object_hash') ) {
790 return spl_object_hash($function[0]) . $function[1];
792 $obj_idx = get_class($function[0]).$function[1];
793 if ( !isset($function[0]->wp_filter_id) ) {
794 if ( false === $priority )
796 $obj_idx .= isset($wp_filter[$tag][$priority]) ? count((array)$wp_filter[$tag][$priority]) : $filter_id_count;
797 $function[0]->wp_filter_id = $filter_id_count;
800 $obj_idx .= $function[0]->wp_filter_id;
805 } else if ( is_string($function[0]) ) {
807 return $function[0] . '::' . $function[1];