tabular.php

<?=
        GridInput::widget([
            'allModels' => $model->orderItems,
            'model' => \app\models\OrderItem::className(),
            'form' => $form,
            'columns' => [
                ['class' => 'mdm\widgets\SerialColumn'],
                [
                    'attribute' => 'name',
                    'widget' => ['kartik\select2\Select2', [
                        // option widget here
                    ]]
                ],
                ['class' => 'mdm\widgets\ButtonColumn']
            ],
            'hiddens'=>[
                'id'
            ]
        ])
        ?>