Yii2 Find all products in parent category

I have 2 tables structure as following:

category(id,cat_name , parent_id);
product(id,category_id ,pro_name);

Relation in Product Model

public function getCategory()
    {
        return $this->hasOne(Category::className(), ['id' => 'category_id']);
    }  

Category

id   cat_name    parent_id
1    Electronic   0
2    Fruit        0
3    TV           1
4    Apple        2

Product
id category_id  pro_name
1  1            Samsung
2  3            Sony
3  3            Panasonic
4  2            Apple
5  2            Orange

What I want to do is when I select on category (1) Electronic I want to get Samsung,Sony,Panasonic from table Product

// given $id is your current toplevel category
$cat_ids = Category::find()->select('id')->where(['parent_id' => $id])->asArray()->all();
$ids = [];
foreach($cat_ids as $value)
{
    $ids[] = $value['id'];
}
$ids = implode(',',$ids);
$categories = Products::find()->where('category_id IN ('.$ids.','.$id.')')->all();

Some object to array functionallity there that you might be able to clean up. This was quick and dirty, but should work. You get the point.