PHP如何識別系統語言或瀏覽器語言

preg_match('/^([a-z\-]+)/i', $_SERVER['HTTP_ACCEPT_LANGUAGE'], $matches);
$lang = $matches[1];
switch ($lang) {
    case 'zh-cn' :
        //header('Location: http://cn.test.com/');
        echo "中國";
        break;
    case 'zh-tw' :
        // header('Location: http://tw.test.com/');
        echo "臺灣";
        break;
    case 'ko' :
        //header('Location: http://ko.test.com/');
        break;
    default:
        // header('Location: http://en.test.com/');
        echo "英文";
        break;
}