apply_filters

Call the functions added to a filter hook.

Description

apply_filters( (string) $tag, (mixed) $value );

The callback functions attached to filter hook $tag 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 $tag parameter.

The function allows for additional arguments to be added and passed to hooks.

return $string;

Parameters (2)

0. $tag (string): The name of the filter hook.
1. $value (mixed): The value on which the filters hooked to $tag are applied on.

Usage

if ( !function_exists( 'apply_filters' ) ) { 
    require_once ABSPATH . WPINC . '/plugin.php'; 
} 
  
// The name of the filter hook. 
$tag = ''; 
  
// The value on which the filters hooked to `$tag` are applied on. 
$value = null; 
  
// NOTICE! Understand what this does before running. 
$result = apply_filters($tag, $value);

Defined (2)

The function is defined in the following location(s).

/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; 
}

/wp-admin/includes/noop.php

function apply_filters() {}