Migrating from FuelPHP to Laravel: problem with one response

i'm migrating an old project from fuel to laravel and i'm having trouble with the response to one of the requests. The issue is, i need the response from laravel to be exactly the same as it was in fuel, because i already have the app in iOS and Android and having the same responses means i only need to change the endpoints. I can't seem to replicate the response here:

• FuelPHP code and response:

      $belongs = Model_Belong::find('all',array(
          'where'=>array(
              array('id_user',$id_user),
          ),
      ));
  
  return $this->createResponse(200, 'List', $belongs);
  *****RESPONSE****
  {
  "code": 200,
  "message": "List",
  "data": {
      "[1][1]": {
          "id_user": 1,
          "id_group": 1
      },
      "[1][2]": {
          "id_user": 1,
          "id_group": 2
      },
      "[1][3]": {
          "id_user": 1,
          "id_group": 3
      }
  }
  }
  
  

• Laravel code and response:

      $belongs = Belong::where('id_user', $id_user)
                  ->get();
  
  return $this->createResponse(200, 'List', $belongs);
  *****RESPONSE*****
  {
  "code": 200,
  "message": "List",
  "data": [
      {
          "id_user": 1,
          "id_group": 1,
      },
      {
          "id_user": 1,
          "id_group": 2,
      },
      {
          "id_user": 1,
          "id_group": 3,
      }
  ]
  }
  
  

Thanks in advance!

via Chebli Mohamed