1.表结构设计

可以用无限极分类，但是用无限级分类没有必要:

1. 查询麻烦,只能查看自己的上级.
2. 查上上级,上上上级需要循环或递归.
3. 事实上不用无限级,3级就足够.

所以表结构可以设计为：

//up
$table->integer('p1')->unsigned()->default(0);
$table->integer('p2')->unsigned()->default(0);
$table->integer('p3')->unsigned()->default(0);
//down
$table->dropColumn('p1');
$table->dropColumn('p2');
$table->dropColumn('p3');

4. 执行迁移文件
php artisan migrate
5. 关注方法进行修改如下

public function guanzhu($message)
    {
        /**
        *获取用户信息
        *将需要信息放到数据库
        *返回回复消息
        */
        $user = new User();//实例化model
        $openid = $message->FromUserName;//获取关注用户的openid
        $fans = $user -> where('openid',$openid) -> first();
        $codeId= false;
        if(isset($message->EventKey)){  //当微信二维码带参数时
            $codeId = substr($message->EventKey,8);
        }
        //判断之前是否关注
        if($fans && $fans->state == 0){ //关注过但是又取消关注了
            $fans->subtime = time();//关注users表的时间
            $fans->state = 1;
            $userService = $this->app->user;//得到用户实例
            $Tuser = $userService->get($openid);//获取用户信息
            $fans->name = $Tuser->nickname;
            $fans->save();
        }elseif(!$fans){ //没有关注过
            $user->openid = $openid;//对应users表的openid
            $user->subtime = time();//关注users表的时间
            $userService = $this->app->user;//得到用户实例
            $Tuser = $userService->get($openid);//获取用户信息
            $user->name = $Tuser->nickname;
            if($codeId){    //当扫描的二维码不带参数时
                //层级关系
                $fans = $user->find($codeId);
                $user->p1 = $codeId;
                $user->p2 = $fans->p1;
                $user->p3 = $fans->p2;
            }
            $user->save();
            //利用uid生成永久性场景二维码，作为用户唯一标示
            $user->code = $this->erCode($user->uid);
            $user->save();      
        }       
        $text = new Text();
        $text->content = '您好！欢迎关注我！';
        return $text;
    }