Yii2: ajax form validation on an ajax submitted form

You should set up validationUrl with a different URL compared to the URL that you are submitting the form to. In this way you can have the validation function that would validate and return the return ActiveForm::validate($model); and the normal submit form that does something else.

You can read more about validationUrl here:

I have found solution :

Form :

 <?php
    $form = ActiveForm::begin(['id' => 'form-add-contact', 'enableAjaxValidation' => true, 'validationUrl' => Yii::$app->urlManager->createUrl('contacts/contacts/contact-validate')]);
    ?>

Submit Via Ajax :

<?php
$script = <<< JS

   $(document).ready(function () { 
        $("#form-add-contact").on('beforeSubmit', function (event) { 
            event.preventDefault();            
            var form_data = new FormData($('#form-add-contact')[0]);
            $.ajax({
                   url: $("#form-add-contact").attr('action'), 
                   dataType: 'JSON',  
                   cache: false,
                   contentType: false,
                   processData: false,
                   data: form_data, //$(this).serialize(),                      
                   type: 'post',                        
                   beforeSend: function() {
                   },
                   success: function(response){                         
                       toastr.success("",response.message);                            
                   },
                   complete: function() {
                   },
                   error: function (data) {
                      toastr.warning("","There may a error on uploading. Try again later");    
                   }
                });                
            return false;
        });
    });       

JS;
$this->registerJs($script);
?>

Controller :

/*
     * CREATE CONTACT FORM  AJAX VALIDATION ACTION
     */

    public function actionContactValidate() {
        $model = new ContactsManagement();
        if (Yii::$app->request->isAjax && $model->load(Yii::$app->request->post())) {
            $model->company_id = Yii::$app->user->identity->company_id;
            $model->created_at = time();
            \Yii::$app->response->format = Response::FORMAT_JSON;
            return ActiveForm::validate($model);
        }
    }


/**
     * Quick Add Contact Action
     * @param type $id
     * @return type
     */
    public function actionAddContact() {           

        $model = new ContactsManagement();

        if (Yii::$app->request->isAjax && $model->load(Yii::$app->request->post())) {

            $transaction = \Yii::$app->db->beginTransaction();

            try {
                if ($model->validate()) {
                    $flag = $model->save(false);
                    if ($flag == true) {
                        $transaction->commit();

                        return Json::encode(array( 'status' => 'success', 'type' => 'success', 'message' => 'Contact created successfully.'));
                    } else {
                        $transaction->rollBack();
                    }
                } else {
                    return Json::encode(array('status' => 'warning', 'type' => 'warning', 'message' => 'Contact can not created.'));
                }
            } catch (Exception $ex) {
                $transaction->rollBack();
            }
        }

        return $this->renderAjax('_add_form', [
                    'model' => $model,
        ]);
    }