apply_filters( string $hook_name, mixed $value, mixed $args )

Calls the callback functions that have been added to a filter hook.


Description

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.

Example usage:

// The filter callback function.
function example_callback( $string, $arg1, $arg2 ) {
    // (maybe) modify $string.
    return $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 );

Parameters

$hook_name

(Required) The name of the filter hook.

$value

(Required) The value to filter.

$args

(Required) Additional parameters to pass to the callback functions.


Return

(mixed) The filtered value after all hooked functions are applied to it.


Source

File: wp-includes/plugin.php

function apply_filters( $tag, $value ) {
	global $wp_filter, $wp_current_filter;

	$args = array();

	// Do 'all' actions first.
	if ( isset($wp_filter['all']) ) {
		$wp_current_filter[] = $tag;
		$args = func_get_args();
		_wp_call_all_hook($args);
	}

	if ( !isset($wp_filter[$tag]) ) {
		if ( isset($wp_filter['all']) )
			array_pop($wp_current_filter);
		return $value;
	}

	if ( !isset($wp_filter['all']) )
		$wp_current_filter[] = $tag;

	if ( empty($args) )
		$args = func_get_args();

	// don't pass the tag name to WP_Hook
	array_shift( $args );

	$filtered = $wp_filter[ $tag ]->apply_filters( $value, $args );

	array_pop( $wp_current_filter );

	return $filtered;
}


Changelog

Changelog
Version Description
6.0.0 Formalized the existing and already documented ...$args parameter by adding it to the function signature.
0.71 Introduced.