public function change_owner($owner)
    {

        if (empty($owner) || !is_int($owner) || $this->owner != getmyuid()) return false;

        if (!empty($this->fp)) fclose($this->fp);

        if (chown($this->path . $this->filename, $owner)) {
            return $this->open($this->path . $this->filename);
        }

        return false;
    }