public function getURL($file_path = null)
    {
        if (!$this->base_url) {
            throw new BaseException('Unable to determine URL');
        }

        if (!$file_path) {
            return $this->base_url;
        }

        $u = $this->base_url;
        if (substr($u, -1) != '/') {
            $u .= '/';
        }

        return $u.$file_path;
    }