How to get parent_id name of category table from post table

Question

I have the following table in the "Category" table.

id	Name	parent_id
1	student	null
2	teacher	null
3	MATHEMATICS STUDENT	1
4	Science Student	1

I have the following table in the "Release" table.

id	Name	category_id
1	阿杰	3
2	Mohan	3

Post.php file in model

public function category(){
            return $this->belongsTo(Category::class, 'category_id', 'id');
  }

If I put the following code, I will get the name of the third id which is math_student.

$post->category->name

But I want to get the name of the parent_id of the category, i.e. - "Student"

I tried the following code but got an error.

$post->category->parent_id->name

Please suggest me a solution

Answer 1

In the category model, add a parent relationship:

public function parent(){
        return $this->belongsTo(Category::class, 'parent_id', 'id')->withDefault();
    }

Then, you can get the parent name

$post->category->parent->name

Answer 2

You need to establish a relationship using parent_id to find the model instance for Category inside it.

In the Category.php model:

public function parent(){
    return $this->belongsTo(Category::class, 'parent_id', 'id');
}

Afterwards, you will be able to:

$post->category->parent->name;