detect language with Willdurand\Negotiation and slim framework

language_detection.php

<?php

use Negotiation\LanguageNegotiator;

// example array
$languages = array(
    1=>array('name'=>'english', 'lang_id'=>'en'),
    2=>array('name'=>'dutch', 'lang_id'=>'nl')
);

$langid2language['en'] = $languages[1];
$langid2language['nl'] = $languages[2];

if (!isset($_SESSION['cms_language_id'])) {
    $lang_negotiator = new LanguageNegotiator();
    $lang_header = $app->request()->headers('ACCEPT_LANGUAGE');

    /** @var Negotiation\AcceptHeader $accept_header */
    $accept_header = $lang_negotiator->getBest($lang_header, array_keys($langid2language));
    if ($accept_header) {
        $lang = $langid2language[$accept_header->getValue()];
    } else {
        // it couldn't be parsed or no header found...
        $lang = current($languages);
    }
    $_SESSION['cms_language_id'] = $lang['id'];
}