ProductImage::rules PHP Method

    public function rules()
    {
        return [['product_id, group_id', 'numerical', 'integerOnly' => true], ['name, title, alt', 'length', 'max' => 250]];
    }

 /**
  * Validate images
  */
 private static function validateImages($images)
 {
     $validator = null;
     foreach ($images as $file) {
         $rules = ProductImage::rules();
         $imagevalidator = Validator::make(array('file' => $file), $rules);
         if ($imagevalidator->fails()) {
             $validator = $imagevalidator;
         }
     }
     return $validator;
 }