mdm\upload\UploadBehavior::__get PHP Method

    public function __get($name)
    {
        if ($name === $this->attribute) {
            if ($this->_file === null) {
                $this->_file = UploadedFile::getInstance($this->owner, $this->attribute);
            }
            return $this->_file;
        } else {
            return parent::__get($name);
        }
    }