php随机字符串

class str{
 public static function quickRandom($length = 16)
    {
        $pool = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';

        return substr(str_shuffle(str_repeat($pool, $length)), 0, $length);
    }
}

echo str::quickRandom();