I have 3 tables:

id | name

1       |      Men >80kg   

2       |      Women >80kg   

3       |      Team Men >80kg   

Category_Tournament (List all categories available in a tournament)

id | category_id | tournament_id

1 | 1 | 2

2 | 2 | 2

3 | 3 | 2

4 | 4 | 2

Category_Tournament_User (categories registered by user)

id | category_tournament_id | user_id

1 | 1 | 201

2 | 3 | 202

Category is the list of categories for all tournaments (C for abreviation)

Category_Tournament is the list of categories the admin configured for this tournament (CT for abreviation)

Category_tournament_User is the categories the user has registred (CTU for abreviation)

User has a list of checkbox that I need to sync with:

        $tournament->categories_user()->sync($categories);

In Tournament Model, I have:

public function categories_user()
{
    return $this->belongsToMany('App\Category','category_tournament_user', 'user_id', 'category_tournament_id')
        ->withTimestamps();
}

Thing is data is syncing in CTU, but instead of inserting user_id, it insert tournament_id.

It probably does it because I'm in Tournament Model.

I tried to put the relationship in User Model, but couldn't make it work neither