protected function unsetCacheHeaders()
    {
        if (empty($this->cdnCacheHeadersSet)) {
            return false;
        }

        // --------------------------------------------------------------------------

        //  Remove previously set headers
        header_remove('Cache-Control');
        header_remove('Last-Modified');
        header_remove('Expires');
        header_remove('ETag');
        header_remove('X-CDN-CACHE');

        // --------------------------------------------------------------------------

        //  Set new "do not cache" headers
        header('Expires: Mon, 26 Jul 1997 05:00:00 GMT', true);
        header('Last-Modified: ' . gmdate('D, d M Y H:i:s') . ' GMT', true);
        header('Cache-Control: no-store, no-cache, must-revalidate', true);
        header('Cache-Control: post-check=0, pre-check=0', false);
        header('Pragma: no-cache', true);
        header('X-CDN-CACHE: MISS', true);

        return true;
    }