protected static function is_modified_file( $filepath ) {

		$actual = filemtime( $filepath );

		$last = isset( self::$files[ $filepath ] ) ? self::$files[ $filepath ] : 0;

		if ( $actual !== $last ) {

			self::$files[ $filepath ] = $actual;

			self::$changes = true;

			return self::$changes;
		}

		return false;
	}