PHP 去掉emoji字符

    function isMatchEmoji($str)
    {
        $pattern='/./u';
        $rs=preg_match_all($pattern,$str,$match);
        if($rs>0){
            foreach($match[0] as $m){
                if(strlen($m) >= 4){
                    return true;
                }
            }
        }
        return false;
    }

    $str='ko