public function actionCreate()
{
    $model = new Order();

    if ($model->load(Yii::$app->request->post())) {
    $transaction = Yii::$app->db->beginTransaction();
    try {
        $success = $model->save();
        if ($success) {
            $model = $this->findModel($model->id);
            $model->orderItems = Yii::$app->request->post('OrderItem', []);
            $success = $model->save();
            if ($success) {
                $transaction->commit();
                return $this->redirect(['view', 'id' => $model->id]);
            }
        }
        $transaction->rollBack();
    } catch (\Exception $ecx) {
        $transaction->rollBack();
        throw $ecx;
    }
    } else {
        return $this->render('create', [
            'model' => $model,
        ]);
    }
}