$from_chr= mb_detect_encoding($user['username'],array('UTF-8','ASCII','EUC-CN','CP936','BIG-5','GB2312','GBK'));

    if($from_chr !="UTF-8")

    {

        $vector = mb_convert_encoding($user['username'],'UTF-8',array('UTF-8','ASCII','EUC-CN','CP936','BIG-5','GB2312','GBK'));

    }