private static function get_filter_callbacks( $filter ) {
		global $wp_filter;

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

		if ( is_a( $wp_filter[ $filter ], 'WP_Hook' ) ) {
			$callbacks = $wp_filter[ $filter ]->callbacks;
		} else {
			$callbacks = $wp_filter[ $filter ];
		}
		if ( is_array( $callbacks ) ) {
			return $callbacks;
		}
		return false;
	}