How can I remove duplicates results when using belongsToMany - laravel

Question

Having the following tables:
----------- ----------------- ---------------
| PROJECT | | ACCESSES | | ENVIRONMENT |
----------- ----------------- ---------------
| id | | id | | id |
| title | | project_id | | title |
----------- | environment_id| ---------------
| username |
| password |
-----------------
My goal is to get all the environments used by a project through the accesses table
In my Project model:
public function environments(){
return $this->belongsToMany('App\Models\Environment', "accesses");
}
My problem is that if I have multiple rows with the same project_id and environment_id values in the accesses table, it will fetch multiple time the same environment.
How may I force it to retrieve each environment only once?

Answer 1

This is an old question, but the benefit of future travellers:
The distinct() method can help in this situation:
public function environments() {
return $this
->belongsToMany('App\Models\Environment', "accesses")
->distinct();
}
From the docs:
The distinct method allows you to force the query to return distinct results:
$users = DB::table('users')->distinct()->get();
As far as I can tell, this works at least as far back as Laravel 4.x, so it should be fine for all currently supported versions.

Answer 2

You can achieve this using sync method or toggle method it depends on your use case.
From the docs:
The many-to-many relationship also provides a toggle method which "toggles" the attachment status of the given IDs. If the given ID is currently attached, it will be detached. Likewise, if it is currently detached, it will be attached:
$project->environments()->toggle([1, 2, 3]);
You may also use the sync method to construct many-to-many associations. The sync method accepts an array of IDs to place on the intermediate table. Any IDs that are not in the given array will be removed from the intermediate table. So, after this operation is complete, only the IDs in the given array will exist in the intermediate table
$project->environments()->sync([1, 2, 3]);
For more information please have a look in the docs.
https://laravel.com/docs/5.6/eloquent-relationships#updating-many-to-many-relationships