php中文正則

$str = '中國人';
//支持utf-8要加u
//$pattern = '/[\x{4e00}-\x{9fa5}]*/iu';
//滿足utf-8和gb2312
$pattern = '/^[a-z\x7f-\xff][\w\x7f-\xff]{1,20}$/i';
$res = preg_match($reg, $str);
echo $res;