php - associate and attach not working? -

i have 2 models : user , favoriteuser

my relationship looks :

user:

public function favorites(){         return $this->hasmany('app\models\favoriteuser', 'user_id');     } 

favorite user:

public function favorite_users()   {     return $this->belongsto('app\models\user');   } 

so how can this:

$user->favorites()->associate($user_id); 

you need have 2 model user , favorite

and declare in user:

public function favorites() {     return $this->belongstomany('app\models\favorite''); } 

and in favorite:

public function users() {     return $this->belongstomany('app\models\user'); } 

and can do:

$user->favorites()->attach($user_id);