private function _get_cache_file_name($request) {

        // iterate through the options associated with the request
        foreach ($request['options'] as $key => $value)

            // ...and remove null or empty values
            if (is_null($value) || $value == '') unset($request['options'][$key]);

        // remove some entries associated with the request
        // callback, arguments and the associated file handler (where it is the case) are not needed
        $request = array_diff_key($request, array('callback' => '', 'arguments' => '', 'file_handler' => ''));

        // return the path and name of the file name associated with the request
        return rtrim($this->cache['path'], '/') . '/' . md5(serialize($request));

    }