has_filter() │ WP 2.5.0

Check 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.

Used By: has_action()
1 time — 0.000043 sec (very fast) | 50000 times — 0.91 sec (very fast) | PHP 7.0.2, WP 4.4.2

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

has_filter( $hook_name, $callback );
$hook_name(string) (required)
The name of the filter hook.
$callback(callable|string|array|false)
The callback to check for. This function can be called unconditionally to speculatively check a callback that may or may not exist.
Default: false

Examples

0

#1 Check if the filter has hooks the_content 

if( has_filter( 'the_content' ) ){
	echo 'There is at least one function attached to `the_content` filter';
}
0

#2 Check if the_content filter has a specific function: 

$priority = has_filter( 'the_content', 'my_function' );
if( $priority ){
	echo "`the_content` filter has my_function() attached with priority $priority";
}

Notes

  • Global. WP_Hook[]. $wp_filter Stores all of the filters and actions.

Changelog

Since 2.5.0 Introduced.

has_filter() code WP 6.5.2

wp-includes/plugin.php 
function has_filter( $hook_name, $callback = false ) {
	global $wp_filter;

	if ( ! isset( $wp_filter[ $hook_name ] ) ) {
		return false;
	}

	return $wp_filter[ $hook_name ]->has_filter( $hook_name, $callback );
}

Filters (hooks)

Hooks (actions, filters)