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WP_Hook::has_filter() public WP 4.7.0

Checks if a specific callback has been registered for this 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.

{} It's a method of the class: WP_Hook{}

No Hooks.

Return

true|false|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.

Usage

$WP_Hook = new WP_Hook();
$WP_Hook->has_filter( $hook_name, $callback );
$hook_name(string)
The name of the filter hook.
Default: ''
$callback(callable|false)
The callback to check for.
Default: false

Changelog

Since 4.7.0 Introduced.

Code of WP_Hook::has_filter() WP 5.8

<?php
public function has_filter( $hook_name = '', $callback = false ) {
	if ( false === $callback ) {
		return $this->has_filters();
	}

	$function_key = _wp_filter_build_unique_id( $hook_name, $callback, false );

	if ( ! $function_key ) {
		return false;
	}

	foreach ( $this->callbacks as $priority => $callbacks ) {
		if ( isset( $callbacks[ $function_key ] ) ) {
			return $priority;
		}
	}

	return false;
}