* The plugin API is located in this file, which allows for creating actions
* and filters and hooking functions, and methods. The functions or methods will
* then be run when the action or filter is called.
* The API callback examples reference functions, but can be methods of classes.
* To hook methods, you'll need to pass an array one of two ways.
* Any of the syntaxes explained in the PHP documentation for the
* {@link https://www.php.net/manual/en/language.pseudo-types.php#language.types.callback 'callback'}
* Also see the {@link https://developer.wordpress.org/plugins/ Plugin API} for
* more information and examples on how to use a lot of these functions.
* This file should have no external dependencies.
// Initialize the filter globals.
require __DIR__ . '/class-wp-hook.php';
/** @var WP_Hook[] $wp_filter */
/** @var int[] $wp_actions */
/** @var string[] $wp_current_filter */
global $wp_current_filter;
$wp_filter = WP_Hook::build_preinitialized_hooks( $wp_filter );
if ( ! isset( $wp_actions ) ) {
if ( ! isset( $wp_current_filter ) ) {
$wp_current_filter = array();
* Hook a function or method to a specific filter action.
* WordPress offers filter hooks to allow plugins to modify
* various types of internal data at runtime.
* A plugin can modify data by binding a callback to a filter hook. When the filter
* is later applied, each bound callback is run in order of priority, and given
* the opportunity to modify a value by returning a new value.
* The following example shows how a callback function is bound to a filter hook.
* Note that `$example` is passed to the callback, (maybe) modified, then returned:
* function example_callback( $example ) {
* // Maybe modify $example in some way.
* add_filter( 'example_filter', 'example_callback' );
* Bound callbacks can accept from none to the total number of arguments passed as parameters
* in the corresponding apply_filters() call.
* In other words, if an apply_filters() call passes four total arguments, callbacks bound to
* it can accept none (the same as 1) of the arguments or up to four. The important part is that
* the `$accepted_args` value must reflect the number of arguments the bound callback *actually*
* opted to accept. If no arguments were accepted by the callback that is considered to be the
* same as accepting 1 argument. For example:
* $value = apply_filters( 'hook', $value, $arg2, $arg3 );
* // Accepting zero/one arguments.
* function example_callback() {
* add_filter( 'hook', 'example_callback' ); // Where $priority is default 10, $accepted_args is default 1.
* // Accepting two arguments (three possible).
* function example_callback( $value, $arg2 ) {
* return $maybe_modified_value;
* add_filter( 'hook', 'example_callback', 10, 2 ); // Where $priority is 10, $accepted_args is 2.
* *Note:* The function will return true whether or not the callback is valid.
* It is up to you to take care. This is done for optimization purposes, so
* everything is as quick as possible.
* @global WP_Hook[] $wp_filter A multidimensional array of all hooks and the callbacks hooked to them.
* @param string $tag The name of the filter to hook the $function_to_add callback to.
* @param callable $function_to_add The callback to be run when the filter is applied.
* @param int $priority Optional. Used to specify 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. Default 10.
* @param int $accepted_args Optional. The number of arguments the function accepts. Default 1.
function add_filter( $tag, $function_to_add, $priority = 10, $accepted_args = 1 ) {
if ( ! isset( $wp_filter[ $tag ] ) ) {
$wp_filter[ $tag ] = new WP_Hook();
$wp_filter[ $tag ]->add_filter( $tag, $function_to_add, $priority, $accepted_args );
* Checks if any filter has been registered for a hook.
* When using the `$function_to_check` argument, this function may return a non-boolean value
* that evaluates to false (e.g. 0), so use the `===` operator for testing the return value.
* @global WP_Hook[] $wp_filter Stores all of the filters and actions.
* @param string $tag The name of the filter hook.
* @param callable|false $function_to_check Optional. The callback to check for. Default false.
* @return bool|int If `$function_to_check` is omitted, returns boolean for whether the hook has
* anything registered. When checking a specific function, the priority of that
* hook is returned, or false if the function is not attached.
function has_filter( $tag, $function_to_check = false ) {
if ( ! isset( $wp_filter[ $tag ] ) ) {
return $wp_filter[ $tag ]->has_filter( $tag, $function_to_check );
* Calls the callback functions that have been added to a filter hook.
* The callback functions attached to the filter hook are invoked by calling
* this function. This function can be used to create a new filter hook by
* simply calling this function with the name of the new hook specified using
* The function also allows for multiple additional arguments to be passed to hooks.
* // The filter callback function.
* function example_callback( $string, $arg1, $arg2 ) {
* // (maybe) modify $string.
* add_filter( 'example_filter', 'example_callback', 10, 3 );
* * Apply the filters by calling the 'example_callback()' function
* * that's hooked onto `example_filter` above.
* * - 'example_filter' is the filter hook.
* * - 'filter me' is the value being filtered.
* * - $arg1 and $arg2 are the additional arguments passed to the callback.
* $value = apply_filters( 'example_filter', 'filter me', $arg1, $arg2 );
* @global WP_Hook[] $wp_filter Stores all of the filters and actions.
* @global string[] $wp_current_filter Stores the list of current filters with the current one last.
* @param string $tag The name of the filter hook.
* @param mixed $value The value to filter.
* @param mixed ...$args Additional parameters to pass to the callback functions.
* @return mixed The filtered value after all hooked functions are applied to it.
function apply_filters( $tag, $value ) {
global $wp_filter, $wp_current_filter;
// Do 'all' actions first.
if ( isset( $wp_filter['all'] ) ) {
$wp_current_filter[] = $tag;
_wp_call_all_hook( $args );
if ( ! isset( $wp_filter[ $tag ] ) ) {
if ( isset( $wp_filter['all'] ) ) {
array_pop( $wp_current_filter );
if ( ! isset( $wp_filter['all'] ) ) {
$wp_current_filter[] = $tag;
// Don't pass the tag name to WP_Hook.
$filtered = $wp_filter[ $tag ]->apply_filters( $value, $args );
array_pop( $wp_current_filter );
* Calls the callback functions that have been added to a filter hook, specifying arguments in an array.
* @see apply_filters() This function is identical, but the arguments passed to the
* functions hooked to `$tag` are supplied using an array.
* @global WP_Hook[] $wp_filter Stores all of the filters and actions.
* @global string[] $wp_current_filter Stores the list of current filters with the current one last.
* @param string $tag The name of the filter hook.
* @param array $args The arguments supplied to the functions hooked to $tag.
* @return mixed The filtered value after all hooked functions are applied to it.
function apply_filters_ref_array( $tag, $args ) {
global $wp_filter, $wp_current_filter;
// Do 'all' actions first.
if ( isset( $wp_filter['all'] ) ) {
$wp_current_filter[] = $tag;
$all_args = func_get_args(); // phpcs:ignore PHPCompatibility.FunctionUse.ArgumentFunctionsReportCurrentValue.NeedsInspection
_wp_call_all_hook( $all_args );
if ( ! isset( $wp_filter[ $tag ] ) ) {
if ( isset( $wp_filter['all'] ) ) {
array_pop( $wp_current_filter );
if ( ! isset( $wp_filter['all'] ) ) {
$wp_current_filter[] = $tag;
$filtered = $wp_filter[ $tag ]->apply_filters( $args[0], $args );
array_pop( $wp_current_filter );
* Removes a function from a specified filter hook.
* This function removes a function attached to a specified filter hook. This
* method can be used to remove default functions attached to a specific filter
* hook and possibly replace them with a substitute.
* To remove a hook, the $function_to_remove and $priority arguments must match
* when the hook was added. This goes for both filters and actions. No warning
* will be given on removal failure.
* @global WP_Hook[] $wp_filter Stores all of the filters and actions.
* @param string $tag The filter hook to which the function to be removed is hooked.
* @param callable $function_to_remove The name of the function which should be removed.
* @param int $priority Optional. The priority of the function. Default 10.
* @return bool Whether the function existed before it was removed.
function remove_filter( $tag, $function_to_remove, $priority = 10 ) {
if ( isset( $wp_filter[ $tag ] ) ) {
$r = $wp_filter[ $tag ]->remove_filter( $tag, $function_to_remove, $priority );
if ( ! $wp_filter[ $tag ]->callbacks ) {
unset( $wp_filter[ $tag ] );
* Remove all of the hooks from a filter.
* @global WP_Hook[] $wp_filter Stores all of the filters and actions.
* @param string $tag The filter to remove hooks from.
* @param int|false $priority Optional. The priority number to remove. Default false.
* @return true True when finished.
function remove_all_filters( $tag, $priority = false ) {
if ( isset( $wp_filter[ $tag ] ) ) {
$wp_filter[ $tag ]->remove_all_filters( $priority );
if ( ! $wp_filter[ $tag ]->has_filters() ) {
unset( $wp_filter[ $tag ] );
* Retrieve the name of the current filter or action.
* @global string[] $wp_current_filter Stores the list of current filters with the current one last
* @return string Hook name of the current filter or action.
function current_filter() {
global $wp_current_filter;
return end( $wp_current_filter );
* Retrieve the name of the current action.
* @return string Hook name of the current action.
function current_action() {
* Retrieve the name of a filter currently being processed.
* The function current_filter() only returns the most recent filter or action
* being executed. did_action() returns true once the action is initially
* This function allows detection for any filter currently being
* executed (despite not being the most recent filter to fire, in the case of
* hooks called from hook callbacks) to be verified.
* @global string[] $wp_current_filter Current filter.
* @param null|string $filter Optional. Filter to check. Defaults to null, which
* checks if any filter is currently being run.
* @return bool Whether the filter is currently in the stack.
function doing_filter( $filter = null ) {
global $wp_current_filter;
if ( null === $filter ) {
return ! empty( $wp_current_filter );
return in_array( $filter, $wp_current_filter, true );
* Retrieve the name of an action currently being processed.
* @param string|null $action Optional. Action to check. Defaults to null, which checks
* if any action is currently being run.
* @return bool Whether the action is currently in the stack.
function doing_action( $action = null ) {
return doing_filter( $action );
* Hooks a function on to a specific action.
* Actions are the hooks that the WordPress core launches at specific points
* during execution, or when specific events occur. Plugins can specify that
* one or more of its PHP functions are executed at these points, using the
* @param string $tag The name of the action to which the $function_to_add is hooked.
* @param callable $function_to_add The name of the function you wish to be called.
* @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.
* @param int $accepted_args Optional. The number of arguments the function accepts. Default 1.
* @return true Will always return true.
function add_action( $tag, $function_to_add, $priority = 10, $accepted_args = 1 ) {
return add_filter( $tag, $function_to_add, $priority, $accepted_args );
* Execute functions hooked on a specific action hook.
* This function invokes all functions attached to action hook `$tag`. It is
* possible to create new action hooks by simply calling this function,
* specifying the name of the new hook using the `$tag` parameter.
* You can pass extra arguments to the hooks, much like you can with `apply_filters()`.
* // The action callback function.
* function example_callback( $arg1, $arg2 ) {
* // (maybe) do something with the args.
* add_action( 'example_action', 'example_callback', 10, 2 );
* * Trigger the actions by calling the 'example_callback()' function
* * that's hooked onto `example_action` above.
* * - 'example_action' is the action hook.
* * - $arg1 and $arg2 are the additional arguments passed to the callback.
* $value = do_action( 'example_action', $arg1, $arg2 );
* @since 5.3.0 Formalized the existing and already documented `...$arg` parameter
* by adding it to the function signature.
* @global WP_Hook[] $wp_filter Stores all of the filters and actions.
* @global int[] $wp_actions Stores the number of times each action was triggered.
* @global string[] $wp_current_filter Stores the list of current filters with the current one last.
* @param string $tag The name of the action to be executed.
* @param mixed ...$arg Optional. Additional arguments which are passed on to the
* functions hooked to the action. Default empty.
function do_action( $tag, ...$arg ) {
global $wp_filter, $wp_actions, $wp_current_filter;
if ( ! isset( $wp_actions[ $tag ] ) ) {
// Do 'all' actions first.
if ( isset( $wp_filter['all'] ) ) {
$wp_current_filter[] = $tag;
$all_args = func_get_args(); // phpcs:ignore PHPCompatibility.FunctionUse.ArgumentFunctionsReportCurrentValue.NeedsInspection
_wp_call_all_hook( $all_args );
if ( ! isset( $wp_filter[ $tag ] ) ) {
if ( isset( $wp_filter['all'] ) ) {
array_pop( $wp_current_filter );
if ( ! isset( $wp_filter['all'] ) ) {
$wp_current_filter[] = $tag;
} elseif ( is_array( $arg[0] ) && 1 === count( $arg[0] ) && isset( $arg[0][0] ) && is_object( $arg[0][0] ) ) {
// Backward compatibility for PHP4-style passing of `array( &$this )` as action `$arg`.
$wp_filter[ $tag ]->do_action( $arg );
array_pop( $wp_current_filter );
* Retrieve the number of times an action is fired.
* @global int[] $wp_actions Stores the number of times each action was triggered.
* @param string $tag The name of the action hook.
* @return int The number of times action hook $tag is fired.
function did_action( $tag ) {
It is recommended that you Edit text format, this type of Fix handles quite a lot in one request
