* 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 int[] $wp_filters */
/** @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_filters ) ) {
if ( ! isset( $wp_current_filter ) ) {
$wp_current_filter = array();
* Adds a callback function to a filter hook.
* WordPress offers filter hooks to allow plugins to modify
* various types of internal data at runtime.
* A plugin can modify data by binding a callback to a filter hook. When the filter
* is later applied, each bound callback is run in order of priority, and given
* the opportunity to modify a value by returning a new value.
* The following example shows how a callback function is bound to a filter hook.
* Note that `$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 $hook_name The name of the filter to add the callback to.
* @param callable $callback 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 filter 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 filter. Default 10.
* @param int $accepted_args Optional. The number of arguments the function accepts. Default 1.
* @return true Always returns true.
function add_filter( $hook_name, $callback, $priority = 10, $accepted_args = 1 ) {
if ( ! isset( $wp_filter[ $hook_name ] ) ) {
$wp_filter[ $hook_name ] = new WP_Hook();
$wp_filter[ $hook_name ]->add_filter( $hook_name, $callback, $priority, $accepted_args );
* Calls the callback functions that have been added to a filter hook.
* This function invokes all functions attached to filter hook `$hook_name`.
* It is possible to create new filter hooks by simply calling this function,
* specifying the name of the new hook using the `$hook_name` parameter.
* 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, $arg2 );
* @since 6.0.0 Formalized the existing and already documented `...$args` parameter
* by adding it to the function signature.
* @global WP_Hook[] $wp_filter Stores all of the filters and actions.
* @global int[] $wp_filters Stores the number of times each filter was triggered.
* @global string[] $wp_current_filter Stores the list of current filters with the current one last.
* @param string $hook_name The name of the filter hook.
* @param mixed $value The value to filter.
* @param mixed ...$args Optional. Additional parameters to pass to the callback functions.
* @return mixed The filtered value after all hooked functions are applied to it.
function apply_filters( $hook_name, $value, ...$args ) {
global $wp_filter, $wp_filters, $wp_current_filter;
if ( ! isset( $wp_filters[ $hook_name ] ) ) {
$wp_filters[ $hook_name ] = 1;
++$wp_filters[ $hook_name ];
// Do 'all' actions first.
if ( isset( $wp_filter['all'] ) ) {
$wp_current_filter[] = $hook_name;
$all_args = func_get_args(); // phpcs:ignore PHPCompatibility.FunctionUse.ArgumentFunctionsReportCurrentValue.NeedsInspection
_wp_call_all_hook( $all_args );
if ( ! isset( $wp_filter[ $hook_name ] ) ) {
if ( isset( $wp_filter['all'] ) ) {
array_pop( $wp_current_filter );
if ( ! isset( $wp_filter['all'] ) ) {
$wp_current_filter[] = $hook_name;
// Pass the value to WP_Hook.
array_unshift( $args, $value );
$filtered = $wp_filter[ $hook_name ]->apply_filters( $value, $args );
array_pop( $wp_current_filter );
* Calls the callback functions that have been added to a filter hook, specifying arguments in an array.
* @see apply_filters() This function is identical, but the arguments passed to the
* functions hooked to `$hook_name` are supplied using an array.
* @global WP_Hook[] $wp_filter Stores all of the filters and actions.
* @global int[] $wp_filters Stores the number of times each filter was triggered.
* @global string[] $wp_current_filter Stores the list of current filters with the current one last.
* @param string $hook_name The name of the filter hook.
* @param array $args The arguments supplied to the functions hooked to `$hook_name`.
* @return mixed The filtered value after all hooked functions are applied to it.
function apply_filters_ref_array( $hook_name, $args ) {
global $wp_filter, $wp_filters, $wp_current_filter;
if ( ! isset( $wp_filters[ $hook_name ] ) ) {
$wp_filters[ $hook_name ] = 1;
++$wp_filters[ $hook_name ];
// Do 'all' actions first.
if ( isset( $wp_filter['all'] ) ) {
$wp_current_filter[] = $hook_name;
$all_args = func_get_args(); // phpcs:ignore PHPCompatibility.FunctionUse.ArgumentFunctionsReportCurrentValue.NeedsInspection
_wp_call_all_hook( $all_args );
if ( ! isset( $wp_filter[ $hook_name ] ) ) {
if ( isset( $wp_filter['all'] ) ) {
array_pop( $wp_current_filter );
if ( ! isset( $wp_filter['all'] ) ) {
$wp_current_filter[] = $hook_name;
$filtered = $wp_filter[ $hook_name ]->apply_filters( $args[0], $args );
array_pop( $wp_current_filter );
* Checks if any filter has been registered for a hook.
* When using the `$callback` 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 $hook_name The name of the filter hook.
* @param callable|string|array|false $callback Optional. The callback to check for.
* This function can be called unconditionally to speculatively check
* a callback that may or may not exist. Default false.
* @return bool|int If `$callback` 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( $hook_name, $callback = false ) {
if ( ! isset( $wp_filter[ $hook_name ] ) ) {
return $wp_filter[ $hook_name ]->has_filter( $hook_name, $callback );
* Removes a callback function from a filter hook.
* This can be used to remove default functions attached to a specific filter
* hook and possibly replace them with a substitute.
* To remove a hook, the `$callback` 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 $hook_name The filter hook to which the function to be removed is hooked.
* @param callable|string|array $callback The callback to be removed from running when the filter is applied.
* This function can be called unconditionally to speculatively remove
* a callback that may or may not exist.
* @param int $priority Optional. The exact priority used when adding the original
* filter callback. Default 10.
* @return bool Whether the function existed before it was removed.
function remove_filter( $hook_name, $callback, $priority = 10 ) {
if ( isset( $wp_filter[ $hook_name ] ) ) {
$r = $wp_filter[ $hook_name ]->remove_filter( $hook_name, $callback, $priority );
if ( ! $wp_filter[ $hook_name ]->callbacks ) {
unset( $wp_filter[ $hook_name ] );
* Removes all of the callback functions from a filter hook.
* @global WP_Hook[] $wp_filter Stores all of the filters and actions.
* @param string $hook_name The filter to remove callbacks from.
* @param int|false $priority Optional. The priority number to remove them from.
* @return true Always returns true.
function remove_all_filters( $hook_name, $priority = false ) {
if ( isset( $wp_filter[ $hook_name ] ) ) {
$wp_filter[ $hook_name ]->remove_all_filters( $priority );
if ( ! $wp_filter[ $hook_name ]->has_filters() ) {
unset( $wp_filter[ $hook_name ] );
* Retrieves the name of the current filter hook.
* @global string[] $wp_current_filter Stores the list of current filters with the current one last
* @return string Hook name of the current filter.
function current_filter() {
global $wp_current_filter;
return end( $wp_current_filter );
* Returns whether or not a filter hook is currently being processed.
* The function current_filter() only returns the most recent filter being executed.
* did_filter() returns the number of times a filter has been applied during
* This function allows detection for any filter currently being executed
* (regardless of whether it's 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 string|null $hook_name Optional. Filter hook 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( $hook_name = null ) {
global $wp_current_filter;
if ( null === $hook_name ) {
return ! empty( $wp_current_filter );
return in_array( $hook_name, $wp_current_filter, true );
* Retrieves the number of times a filter has been applied during the current request.
* @global int[] $wp_filters Stores the number of times each filter was triggered.
* @param string $hook_name The name of the filter hook.
* @return int The number of times the filter hook has been applied.
function did_filter( $hook_name ) {
if ( ! isset( $wp_filters[ $hook_name ] ) ) {
return $wp_filters[ $hook_name ];
* Adds a callback function to an action hook.
* 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 $hook_name The name of the action to add the callback to.
* @param callable $callback The callback to be run when the action is called.
* @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.
* @return true Always returns true.
function add_action( $hook_name, $callback, $priority = 10, $accepted_args = 1 ) {
return add_filter( $hook_name, $callback, $priority, $accepted_args );
* Calls the callback functions that have been added to an action hook.
* This function invokes all functions attached to action hook `$hook_name`.
* It is possible to create new action hooks by simply calling this function,
* specifying the name of the new hook using the `$hook_name` 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.
* 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 $hook_name The name of the action to be executed.
* @param mixed ...$arg Optional. Additional arguments which are passed on to the
* functions hooked to the action. Default empty.
function do_action( $hook_name, ...$arg ) {
global $wp_filter, $wp_actions, $wp_current_filter;
if ( ! isset( $wp_actions[ $hook_name ] ) ) {
$wp_actions[ $hook_name ] = 1;
++$wp_actions[ $hook_name ];
// Do 'all' actions first.
if ( isset( $wp_filter['all'] ) ) {
$wp_current_filter[] = $hook_name;
$all_args = func_get_args(); // phpcs:ignore PHPCompatibility.FunctionUse.ArgumentFunctionsReportCurrentValue.NeedsInspection
_wp_call_all_hook( $all_args );
if ( ! isset( $wp_filter[ $hook_name ] ) ) {
if ( isset( $wp_filter['all'] ) ) {
array_pop( $wp_current_filter );
It is recommended that you Edit text format, this type of Fix handles quite a lot in one request
