Your category table should be like this: id, parent_id, category_name. Whereas parent_id shows where that category is. For example:

id, parent_id, category_name

1,0,Category 1

2,1,category 1.1

3,2,category 1.1.1

4,0,Category 2

5,4,category 2.1

6,5,category 2.1.1

Every cat. has its unique id, and its parent's id (if its 0 there is no parent)

With this structure if you add a new sub-cat. under "Category 1", sub-cat. gets 7 as id, and also gets 1 as parent_id.

Thanks, so in my Category model i should write something like this:

    public function subcats()
    {
        return $this->belongsToMany('Category', 'parent_id');
    }

that's it?

I'm new at Laravel, so I'm not sure about that :) But the algorithm is OK :)