code: public static function getInstances($model, $attribute)
      {
          $name = Html::getInputName($model, $attribute);
          return static::getInstancesByName($name);
      }
docs: Returns all uploaded files for the given model attribute.
  @param \yii\base\Model $model the data model
  @param string $attribute the attribute name. The attribute name may contain array indexes
  for tabular file uploading, e.g. '[1]file'.
  @return UploadedFile[] array of UploadedFile objects.
  Empty array is returned if no available file was found for the given attribute.