How to get id array of related hasMany models?

Question

Yii

Here are the models in brackets attributes Category (id, title), CatToProd (id, id_category, id_product), Product (id, title)
here are the links in the Product model

public function getCategorys(){
        return $this->hasMany(Category::className(),['id'=>'id_category'])->viaTable('cat_to_prod', ['id_product' => 'id']);
    }

    public function getCatToProd(){
        return $this->hasMany(CatToProd::className(),['id_product' => 'id']);
    }

this is how i try to get category id to use in select2

public function getDataCategory($model){
        $categorys=$model->categorys;
        $arrResult=array();
        foreach ($categorys as $category){
            $arrResult[]=$category->id;
        }
        return $arrResult;
    }

I don't really like this code but how do you get. Get an array like [1,2,3]

Answer 1

public function getDataCategory($model){
       return array_column($model->categorys, 'id');
    }