Simple website with 2 languages (using Twig, Phroute, php Gettext library)

config.php

<?php
require dirname(__FILE__). '/vendor/autoload.php';

use Gettext\Translator;
use Gettext\Translations;

$tplDir = dirname(__FILE__).'/templates/';
$tmpDir = dirname(__FILE__).'/tmp/cache/';
$loader = new Twig_Loader_Filesystem($tplDir);


//Create the translator instance
$I18N = new Translator();

// force auto-reload to always have the latest version of the template
$twig = new Twig_Environment($loader, array(
    'cache' => $tmpDir,
    'auto_reload' => true
));

// add Twig integration for language function
function twig_func_gettext($string) {
    $I18N = $GLOBALS['I18N'];
    return $I18N->gettext($string);
}

$function = new Twig_SimpleFunction('i18n', 'twig_func_gettext');
$twig->addFunction($function);

// Via: https://stackoverflow.com/a/25749660
function prefered_language(array $available_languages, $http_accept_language, $default_lang = "ru") {
    $available_languages = array_flip($available_languages);

    $langs = array();
    preg_match_all('~([\w-]+)(?:[^,\d]+([\d.]+))?~', strtolower($http_accept_language), $matches, PREG_SET_ORDER);
    foreach($matches as $match) {

        list($a, $b) = explode('-', $match[1]) + array('', '');
        $value = isset($match[2]) ? (float) $match[2] : 1.0;

        if(isset($available_languages[$match[1]])) {
            $langs[$match[1]] = $value;
            continue;
        }

        if(isset($available_languages[$a])) {
            $langs[$a] = $value - 0.1;
        }

    }
    if (!$langs) return array($default_lang => 1.0);
    arsort($langs);

    return $langs;
}

$available_languages = array("en", "ru");
$langs = prefered_language($available_languages, $_SERVER["HTTP_ACCEPT_LANGUAGE"], "en");

// get first element of language array
@$lang = array_pop(array_reverse(array_keys($langs)));

// using cookie as preffered language source
if (isset($_COOKIE['lang'])) {
    $lang = $_COOKIE['lang'];
    if (!in_array($lang, $available_languages)) $lang = 'en';
}

$locale = 'en_US';
if ($lang === 'ru') $locale = 'ru_RU';

// gettext have a strange bugs on Windows OS, no way to easy debug it
// so we using php library Gettext
$translations = Translations::fromPoFile(dirname(__FILE__)."/localization/$locale/LC_MESSAGES/localization.po");
$translations->toPhpArrayFile(dirname(__FILE__)."/tmp/$locale.php");

$I18N->loadTranslations(dirname(__FILE__)."/tmp/$locale.php");

$GLOBALS['LANGS'] = $available_languages;
$GLOBALS['I18N'] = $I18N;
$GLOBALS['TWIG'] = $twig;
$GLOBALS['LOCALE'] = $locale;

index.php

<?php
// All non-exists requests must be redirect to Index.php
// Packages must be installed via Composer

require ("config.php");
use Phroute\Phroute\RouteCollector;
use Phroute\Phroute\Dispatcher;

$router = new RouteCollector();

$router->get('/lang/{lang}', function ($lang){
    $available_languages = $GLOBALS['LANGS'];
    if (!in_array($lang, $available_languages)) $lang = 'en';

    setcookie('lang', $lang, time()+60*60, '/', NULL, false, true);
    header("Location: /");
});

$router->get('/{page}?', function($page=null){
    $twig = $GLOBALS['TWIG'];
    $locale = $GLOBALS['LOCALE'];

    if (!$page) return $twig->render('home.html',array('language' => $locale));

    if ($twig->getLoader()->exists("$page.html")) {
        return $twig->render("$page.html",array('language' => $locale));
    }

    // Not found case
    header($_SERVER["SERVER_PROTOCOL"]." 404 Not Found");
    return $twig->render('404.html',array('language' => $locale));
});

$dispatcher =  new Dispatcher($router->getData());
try {
    $response = $dispatcher->dispatch($_SERVER['REQUEST_METHOD'], parse_url($_SERVER['REQUEST_URI'], PHP_URL_PATH));
} catch (Phroute\Phroute\Exception\HttpRouteNotFoundException $ex) {
    $response = $dispatcher->dispatch("GET", "/404.html");
}
echo $response;