Illuminate\Routing\UrlGenerator::replaceRoutableParameters PHP Method

    protected function replaceRoutableParameters($parameters = [])
    {
        $parameters = is_array($parameters) ? $parameters : [$parameters];
        foreach ($parameters as $key => $parameter) {
            if ($parameter instanceof UrlRoutable) {
                $parameters[$key] = $parameter->getRouteKey();
            }
        }
        return $parameters;
    }