protected function isSitemapURL($url)
    {
        $path = parse_url($this->urlEncode($url), PHP_URL_PATH);
        return $this->urlValidate($url) && (
            mb_substr($path, -mb_strlen(self::XML_EXTENSION) - 1) == '.' . self::XML_EXTENSION ||
            mb_substr($path, -mb_strlen(self::XML_EXTENSION_COMPRESSED) - 1) == '.' . self::XML_EXTENSION_COMPRESSED
        );
    }