Php 获取所有属于许多Laravel子类别的文章

我正在尝试显示属于父类别的所有活动

类别模型：

   public function parents()
    {
        return $this->hasMany('App\Category');
    }


    public function categories()
    {
        return $this->belongsTo('App\Category','id','parent_id','categories');
    }


    public function campaigns()
    {
        return $this->belongsToMany('App\Campaign' );
    }

public function categories()
    {
        return $this->belongsToMany('App\Category' , 'campaign_category', 'campaign_id', 'category_id');
    }

活动模式：

   public function parents()
    {
        return $this->hasMany('App\Category');
    }


    public function categories()
    {
        return $this->belongsTo('App\Category','id','parent_id','categories');
    }


    public function campaigns()
    {
        return $this->belongsToMany('App\Campaign' );
    }

public function categories()
    {
        return $this->belongsToMany('App\Category' , 'campaign_category', 'campaign_id', 'category_id');
    }

---

对不起，我刚才做了这个：D

    $campaigns = Campaign::whereHas('categories', function($q) use($id) {
        $q->where('parent_id', '=', $id);
    })->get();

---

对不起，我刚才做了这个：D

    $campaigns = Campaign::whereHas('categories', function($q) use($id) {
        $q->where('parent_id', '=', $id);
    })->get();