code: public static function validateMultiple($models, $attributes = null)
      {
          $result = [];
          /* @var $model Model */
          foreach ($models as $i => $model) {
              $model->validate($attributes);
              foreach ($model->getErrors() as $attribute => $errors) {
                  $result[Html::getInputId($model, "[$i]" . $attribute)] = $errors;
              }
          }
  
          return $result;
      }
docs: Validates an array of model instances and returns an error message array indexed by the attribute IDs.
  This is a helper method that simplifies the way of writing AJAX validation code for tabular input.
  
  For example, you may use the following code in a controller action to respond
  to an AJAX validation request:
  
  ```php
  // ... load $models ...
  if (Yii::$app->request->isAjax) {
  Yii::$app->response->format = Response::FORMAT_JSON;
  return ActiveForm::validateMultiple($models);
  }
  // ... respond to non-AJAX request ...
  ```
  
  @param array $models an array of models to be validated.
  @param mixed $attributes list of attributes that should be validated.
  If this parameter is empty, it means any attribute listed in the applicable
  validation rules should be validated.
  @return array the error message array indexed by the attribute IDs.