I'm trying to create an URL-router, where the website language is defined by the first two chars in the domain.Example:domain.com/en(the site will then display content in English).The script below is what I've come up with so far. Focus is on functionality instead of SEO. However, I would like it to be optimized for both, and honestly I'm no expert at search engine optimization.Would Googlebot be able to index both the English and Danish content? (notice the way I get the visitors language, and make redirects accordingly)Is there anything I could do to improve the script functionality, including SEO handling?All suggestions for improvement are more than welcome.class Router {    private $allowedLang = array('da', 'en');    private $langRouter = array(        'en' => 'en_US',        'da' => 'da_DK'    );    function __construct() {        $locale = in_array($_GET['locale'], $this->allowedLang);        if ($locale) {            // If get-var locale is allowed, set it as session            $_SESSION['language'] = $_GET['locale'];        }        if (empty($_SESSION['language'])) {            // If session isn't set, use visitor's browser language            $_SESSION['language'] = $this->getLanguage();        }        // Only redirect if get-var locale is empty or isn't allowed, and target file is not located in lib folder (ajax files etc.)        if ((empty($_GET['locale']) || !$locale) && substr($_SERVER['SCRIPT_NAME'], 0, 4) != '/lib') {            header('Location: /'.$_SESSION['language']);        }        $this->setLanguage($_SESSION['language']);    }    public function setLanguage($lang) {        // If $lang is allowed use it, else default to DEFAULT_LANGUAGE        $locale = (in_array($lang, $this->allowedLang) ? $this->langRouter[$lang] : DEFAULT_LANGUAGE);        // Initiate gettext        putenv(LC_ALL=$locale);        setlocale(LC_ALL, $locale);        bindtextdomain(messages, CLIENT_PATH./lib/locale);        textdomain(messages);    }    /**     * Get the visitor's language based on browser settings.     * If language isn't found or isn't allowed, default to DEFAULT_LANGUAGE     */    private function getLanguage() {        if (isset($_SERVER['HTTP_ACCEPT_LANGUAGE'])) {            $langs = explode(',',$_SERVER['HTTP_ACCEPT_LANGUAGE']);            foreach ($langs as $value) {                $choice = substr($value, 0, 2);                if (in_array($choice, $this->allowedLang)) {                    return $choice;                }            }        }        return DEFAULT_LANGUAGE;    }}
Optimizing URL router behaviour
php;optimization;http;url