Stikked/htdocs/application/hooks/pick_language.php

<?php defined('BASEPATH') OR exit('No direct script access allowed.');
/**
 * Determines the language to use.
 *
 * This is called from the Codeigniter hook system.
 * The hook is defined in application/config/hooks.php
 */
function pick_language() {

    require APPPATH . '/config/language.php';

    // Re-populate $_GET
    parse_str($_SERVER['QUERY_STRING'], $_GET);

    // Lang set in URL via ?lang=something
    if (!empty($_GET['lang'])) {
        // Turn en-gb into en
        $lang = strtolower(substr($_GET['lang'], 0, 2));
    }
    // Lang has already been set and is stored in a session
    elseif (!empty($_SESSION['lang_code'])) {
        $lang = $_SESSION['lang_code'];
    }
    // Lang has is picked by a user.
    elseif (!empty($_COOKIE['lang_code'])) {
        $lang = strtolower($_COOKIE['lang_code']);
    }

    // Still no Lang. Lets try some browser detection then
    elseif (!empty($_SERVER['HTTP_ACCEPT_LANGUAGE'])) {
        // explode languages into array
        $accept_langs = explode(',', $_SERVER['HTTP_ACCEPT_LANGUAGE']);
        $supported_langs = array_keys($config['supported_languages']);
        // Check them all, until we find a match
        foreach ($accept_langs as $accept_lang) {
            if (strpos($accept_lang, '-') === 2) {
                // Turn pt-br into br
                $lang = strtolower(substr($accept_lang, 3, 2));
                // Check its in the array. If so, break the loop, we have one!
                if (in_array($lang, $supported_langs)) {
                    break;
                }
            }
            // Turn en-gb into en
            $lang = strtolower(substr($accept_lang, 0, 2));
            // Check its in the array. If so, break the loop, we have one!
            if (in_array($lang, $supported_langs)) {
                break;
            }
        }
    }

    // If no language has been worked out - or it is not supported - use the default
    if (empty($lang) OR !array_key_exists($lang, $config['supported_languages'])) {
        $lang = $config['default_language'];
    }

    // Whatever we decided the lang was, save it for next time to avoid working it out again
    $_SESSION['lang_code'] = $lang;

    // Load CI config class
    $CI_config = & load_class('Config');

    // Set the language config. Selects the folder name from its key of 'en'
    $CI_config->set_item('language', $config['supported_languages'][$lang]['folder']);

    // Sets a constant to use throughout ALL of CI.
    define('AUTO_LANGUAGE', $lang);
}