controllers/AdminController.php
protected function performAjaxValidation($models)
    {
        if (\Yii::$app->request->isAjax) {
            if (is_array($models)) {
                $result = [];
                foreach ($models as $model) {
                    if ($model->load(\Yii::$app->request->post())) {
                        \Yii::$app->response->format = Response::FORMAT_JSON;
                        $result = array_merge($result, ActiveForm::validate($model));
                    }
                }
                echo json_encode($result);
                \Yii::$app->end();
            } else {
                if ($models->load(\Yii::$app->request->post())) {
                    \Yii::$app->response->format = Response::FORMAT_JSON;
                    echo json_encode(ActiveForm::validate($models));
                    \Yii::$app->end();
                }
            }
        }
    }
protected function performAjaxValidation($models)
    {
        if (\Yii::$app->request->isAjax) {
            if (is_array($models)) {
                $result = [];
                foreach ($models as $model) {
                    if ($model->load(\Yii::$app->request->post())) {
                        \Yii::$app->response->format = Response::FORMAT_JSON;
                        $result = array_merge($result, ActiveForm::validate($model));
                    }
                }
                echo json_encode($result);
                \Yii::$app->end();
            } else {
                if ($models->load(\Yii::$app->request->post())) {
                    \Yii::$app->response->format = Response::FORMAT_JSON;
                    echo json_encode(ActiveForm::validate($models));
                    \Yii::$app->end();
                }
            }
        }
    }
Performs AJAX validation.
@param array|Model $models
@throws \yii\base\ExitException