private function prepareUrl(array $url): array
    {
        // collect the pass parameters of the url under "pass" key for router.js compatibility
        $pass = [];
        foreach ($url as $key => $value) {
            if (is_int($key)) {
                $pass[$key] = $value;
                unset($url[$key]);
            }
        }
        $url['pass'] = $pass;

        return $url;
    }