Отправка данных ActiveForm с помощью Ajax (с пост-оберткой)

gistfile1.txt

Контроллер ClientController:
============================

  public function actionAdd()
  {
      $model = new AddClientOwnerForm();
      if(Yii::$app->request->isAjax){
          if($model->load(Yii::$app->request->post())) {
              // ... ваш обработчик данных...
              if ($model->save()) {
                  return '<option value="'.$model->id.'">'.$model->fio.' ('.$model->phone.','.$model->email.')</option>';
              } else {
                  return '<script>alert("Ошибка добавления в БД")</script>';
              }
          }
      }
  }
  
Вьюха form.php:
============================

<?php $form = ActiveForm::begin(['action' => ['client/add'], 'method' => 'post', 'id' => 'form-client-add']); ?>
<div class="modal-body">
    <?= $form->field($clientModel, 'fio')->textInput(['maxlength' => true, 'placeholder' => 'Иванов Иван']) ?>
    <?= $form->field($clientModel, 'phone')->textInput(['maxlength' => true, 'placeholder' => '89101234567']) ?>
    <?= $form->field($clientModel, 'email')->textInput(['maxlength' => true, 'placeholder' => 'почта_собственника@mail.ru']) ?>
    <?= $form->field($clientModel, 'category')->dropDownList(Client::getCategoryOwnerArray()) ?>
    <?= $form->field($clientModel, 'city_id')->dropDownList(City::getCityList()) ?>
</div>
<div class="modal-footer">
    <?= Html::submitButton('<i class="fa fa-save"></i> Добавить', ['class' => 'btn btn-warning', 'id' => 'btn-client-add']) ?>
</div>
<?php ActiveForm::end(); ?>

<?php
$js = <<<JS
    $('#form-client-add').on('beforeSubmit', function(){
         
        var data = $(this).serialize();
         
        $.ajax({
            url: '/client/add',
            type: 'POST',
            data: data,
            success: function(res){
                $('#addclientownerform-fio').val('');
                $('#addclientownerform-phone').val('');
                $('#addclientownerform-email').val('');
                $('#addClientModal').modal('hide');
                $('#object-client_id').append(res);
                $("#object-client_id :last").attr("selected", "selected");
            },
            error: function(){
                alert('Error!');
            }
        });
         
        return false;
    });
JS;