/**
     * 产生随机字符串
     * @param int $length
     * @param bool $number
     * @param bool $chars
     * @return string
     */
    public static function createRandomStr($length = 32, $number = false, $chars = false) {
        if (!$chars) {
            $chars = "abcdefghijklmnopqrstuvwxyz0123456789";
            if ($number) $chars = "0123456789";
        }
        $str = "";
        for ($i = 0; $i < $length; $i++) {
            $str .= substr($chars, mt_rand(0, strlen($chars) - 1), 1);
        }
        return $str;
    }

参数解读：

使用示例：

public function login()
{
    $loginCode = ClassName::createRandomStr(3, true);
    // $loginCode = "482"
}

文中的ClassName请替换为自己的文件类名