public static function setUseMultiByte($use_mbstring)
    {
        if ($use_mbstring) {
            if (!extension_loaded(self::$__mbstring_extension_name)) {
                self::toss(
                    "RuntimeException",
                    "The '{0}' extension must be enabled.",
                    self::$__mbstring_extension_name
                );
            }
            self::$use_mbstring = true;
            if (!self::$char_set) {
                self::$char_set = self::getDefaultCharacterSet();
            }
        } else {
            self::$use_mbstring = false;
        }
    }