PHP生成随机字符串

function randomkeys($length){
        $result = "";
        $pattern='1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLOMNOPQRSTUVWXYZ';
        for($i=0;$i<$length;$i++)
        {
            $result .= $pattern{mt_rand(0,35)};
        }
        return $result;
    }