device - PHP 以判断移动设备跳转，怎么回跳？

<code>require(dirname(__FILE__)."/lib/Mobile_Detect.php");
$detect = new Mobile_Detect;
$deviceType = ($detect->isMobile() ? ($detect->isTablet() ? 'tablet' : 'phone') : 'computer');

if($_SERVER["SERVER_NAME"] == "nj.xxx.cn" ){        
    if($deviceType == "phone") {
        header("Location:http://m.xxx.cn/");
        exit();
    }
}
</code>

<code>require(dirname(__FILE__)."/lib/Mobile_Detect.php");
$detect = new Mobile_Detect;
$deviceType = ($detect->isMobile() ? ($detect->isTablet() ? 'tablet' : 'phone') : 'computer');

if($_SERVER["SERVER_NAME"] == "nj.xxx.cn" ){        
    if($deviceType == "phone") {
        header("Location:http://m.xxx.cn/");
        exit();
    }
}
</code>