thinkphp 菜单表数据的组合

数据表：

model:一级菜单类进行一对多关联

<?php

namespace app\pc\model;

use think\Model;

class FirstLevelMenus extends Model
{
  protected $table = 'first_level_menus';
  protected $pk = 'menu_id';

  public function secondMenus()
    {
        return $this->hasMany(SecondLevelMenus::class,'parent_menu_tag','menu_tag');
    }
}

model/二级菜单空模型

<?php
namespace app\pc\model;
use think\Model;

class SecondLevelMenus extends Model{
    protected $table = 'second_level_menus';
    protected $pk = 'menu_id';
}

在index调用

<?php

declare(strict_types=1);

namespace app\pc\controller;

use app\pc\model\FirstLevelMenus;

class Index
{
    public f