Checks if a specific callback has been registered for this hook.

Description

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.

Parameters

$hook_namestringoptional

The name of the filter hook.

Default:''

$callbackcallable|string|array|falseoptional

The callback to check for.
This method can be called unconditionally to speculatively check a callback that may or may not exist.

Default:false

Return

Source

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;
}

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