final public static function getServerInfo(string $infoname):string
    {
        switch ($infoname) {
            case 'PHP_VERSION':
                $rs = phpversion();
                break;
            default:
                try {
                    $rs = $_SERVER[$infoname];
                } catch (\Exception $e) {
                    throw new Server500(new \ArrayObject(array("explain" =>
                        "Core Error: The server info $infoname does not exist", "solution" => "Check your keyword")));
                }
                break;
        }
        return ($rs);
    }