Select2 does not put all ID in the query

Hi, I have inserted the select and work properly, but if I try to put a multiselect with select2 I have problems.

Controllers:

$articoli = Articoli::find($articleId);
$articoli->id_gioco = $request->get('id_gioco');
$articoli->id_console = $request->get('id_console');

$articoli->save();

Blade:

<select class="col-md-12" name="id_gioco[]" id="id_gioco" multiple>
  <option value="0"> Seleziona un'altra Gioco</option>
  @foreach($giochi as $gioco)
  <option value="{{ $gioco->id }}"
    @if ($articoli->id_gioco == $gioco->id)
    selected="selected"
    @endif
    >{{ $gioco->nome }}</option>
    @endforeach
</select>

As you can see from the screen, select2 works: https://pasteboard.co/3wftqvvHt.png

Unfortunately, however, I get this error:

(2/2) QueryException
Array to string conversion (SQL: update `articoli` set `id_console` = 4, `updated_at` = 2017-06-30 20:43:30, `id_gioco` = 1129 where `id` = 5675)

Why does not I print both ID?

The correct query should be:

UPDATE `articoli` SET `id_console` = '4,8', `id_gioco` = '1129,1784' WHERE `articoli`.`id` = 5675