lang.php

<?php
if ( $_GET ) {
    $lang = set_lang( key($_GET) );
} else if ( isset($_COOKIE['lang']) ) {
    $lang = $_COOKIE['lang'];
} else {
    $lang = set_lang( substr( $_SERVER['HTTP_ACCEPT_LANGUAGE'], 0, 2) );
}

function set_lang( $l ) {
    switch ( $l ) {
        case 'de':
            break;
        case 'fr':
            break;
        default:
            $l = 'en';
    }
    setcookie('lang', $l, time()+3600, '/');
    return $l;
}

Simple language selection for On-Pager to use with e.g. Bootstrap.