Мультиязычность

Подскажите, пожалуйста, как правильно впилить мультиязычность.
В строке адреса \домен\lang\controller\action\id, если нет lang - редирект на "правильный" адрес. Язык по-умолчанию - вызов константы Config::SITE_LANGUAGE
Второй день траю, никак не идёт

index.php

ini_set('error_reporting', E_ALL);
require_once dirname(__DIR__) . '/vendor/twig/twig/lib/Twig/Autoloader.php';
Twig_Autoloader::register();
spl_autoload_register(function ($class) {
    $root = dirname(__DIR__);
    $file = $root . '/' . str_replace('\\', '/', $class) . '.php';
    if (is_readable($file)) {
        require_once $file;
    }
});
set_error_handler('Core\Error::errorHandler');
set_exception_handler('Core\Error::exceptionHandler');
$router = new Core\Router();
$router->addRoutes('', ['controller' => 'Home', 'action' => 'index']);
$router->addRoutes('{controller}',  ['action' => 'index']);
$router->addRoutes('{controller}/', ['action' => 'index']);
$router->addRoutes('{controller}/{action}');
$router->addRoutes('{controller}/{action}/');
$router->addRoutes('{controller}/{action}/{id:\d+}');
$router->addRoutes('{controller}/{action}/{id:\d+}/');
$router->dispatch($_SERVER['QUERY_STRING']);

router.php

namespace Core;
/**
 * Class Router
 * @package Core
 */
class Router
{
    protected $routes = [];
    protected $parameters = [];
    /**
     * @param $route
     * @param array $parameters
     */
    public function addRoutes($route, $parameters = [])
    {
        $route = preg_replace('/\//', '\\/', $route);
        $route = preg_replace('/\{([a-z]+)\}/', '(?P<\1>[a-z-]+)', $route);
        $route = preg_replace('/\{([a-z]+):([^\}]+)\}/', '(?P<\1>\2)', $route);
        $route = '/^' . $route . '$/i';
        $this  -> routes[$route] = $parameters;
    }
    /**
     * @return array
     */
    public function getRoutes()
    {
        return $this -> routes;
    }
    /**
     * @return array
     */
    public function getParameters()
    {
        return $this -> parameters;
    }
    /**
     * @param $url
     * @throws \Exception
     */
    public function dispatch($url)
    {
        $url = $this->removeQueryStringVariables($url);
        if ($this->matchRoutes($url)) {
            $controller = $this -> parameters['controller'] . 'Controller';
            $controller = $this -> convertToStudlyCaps($controller);
            $controller = $this -> getNamespaces() . $controller;
            if (class_exists($controller)) {
                $controller_object = new $controller($this -> parameters);
                $action = $this -> parameters['action'];
                $action = $this -> convertToCamelCase($action);
                if (is_callable([$controller_object, $action]) && !isset($this -> parameters['id'])) {
                    $controller_object -> $action();
                }
                elseif (is_callable([$controller_object, $action]) && isset($this -> parameters['id'])) {
                    $id = $this -> parameters['id'];
                    $controller_object -> $action($id);
                }
                else {
                    throw new \Exception("Метода $action (в контроллере $controller_object) нет");
                }
            } else {
                throw new \Exception("Контроллер $controller не найден");
            }
        } else {
            throw new \Exception('Роута нет', 404);
        }
    }
    /**
     * @param $url
     * @return string
     */
    protected function removeQueryStringVariables($url)
    {
        if ($url != '') {
            $parts = explode('&', $url, 2);
            if (strpos($parts[0], '=') === false) {
                $url = $parts[0];
            } else {
                $url = '';
            }
        }
        return $url;
    }
    /**
     * @param $url
     * @return bool
     */
    public function matchRoutes($url)
    {
        foreach ($this -> routes as $route => $parameters) {
            if (preg_match($route, $url, $matches)) {
                foreach ($matches as $key => $match) {
                    if (is_string($key)) {
                        $parameters[$key] = $match;
                    }
                }
                $this -> parameters = $parameters;
                return true;
            }
        }
    }
    /**
     * @param $string
     * @return mixed
     */
    protected function convertToStudlyCaps($string)
    {
        return str_replace(' ', '', ucwords(str_replace('-', ' ', $string)));
    }
    /**
     * @return string
     */
    protected function getNamespaces()
    {
        $namespace = 'App\Controllers\\';
        if (array_key_exists('namespace', $this -> parameters)) {
            $namespace .= $this -> parameters['namespace'] . '\\';
        }
        return $namespace;
    }
    /**
     * @param $string
     * @return string
     */
    protected function convertToCamelCase($string)
    {
        return lcfirst($this -> convertToStudlyCaps($string));
    }
}