code: public static function getInstanceByName($name)
      {
          $files = self::loadFiles();
          return isset($files[$name]) ? new static($files[$name]) : null;
      }
docs: Returns an uploaded file according to the given file input name.
  The name can be a plain string or a string like an array element (e.g. 'Post[imageFile]', or 'Post[0][imageFile]').
  @param string $name the name of the file input field.
  @return null|UploadedFile the instance of the uploaded file.
  Null is returned if no file is uploaded for the specified name.