How can I clean this 'controller' file in this mini-php-framework with deals with multilingual websites

Question

I came up with a mini-framework which deals with multilingual websites without using Gettext or Zend_Translate by joining together very good answers from previous questions I asked like this one.

languages/lang.en.php(the multilingual content source):

<?php
$lang = array(
    'tagline_h2' => 'I create <a href="#content">websites</a>...',

languages/lang.es.php(the multilingual content source in other language):

<?php
$lang = array(
    'tagline_h2' => 'Creo <a href="#content">sitios webs</a>...',

common.php (the controller of the content source):

<?php
session_start();
header('Cache-control: private'); // IE 6 FIX

if(isSet($_GET['lang']))
{
$lang = $_GET['lang'];

// register the session and set the cookie
$_SESSION['lang'] = $lang;

setcookie("lang", $lang, time() + (3600 * 24 * 30));
}
else if(isSet($_SESSION['lang']))
{
$lang = $_SESSION['lang'];
}
else if(isSet($_COOKIE['lang']))
{
$lang = $_COOKIE['lang'];
}
else
{
$lang = 'en';
}

//use appropiate lang.xx.php file according to the value of the $lang
switch ($lang) {
  case 'en':
  $lang_file = 'lang.en.php';
  break;

  case 'es':
  $lang_file = 'lang.es.php';
  break;

  case 'tw':
  $lang_file = 'lang.tw.php';
  break;

  case 'cn':
  $lang_file = 'lang.cn.php';
  break;

  default:
  $lang_file = 'lang.en.php';
}

//translation helper function
function lang($translation) {
    global $lang;
    return $lang[$translation]; }

include_once 'languages/'.$lang_file;
?>

index.php (the output):

<div id="tagline">
    <h2><?php echo lang('tagline_h2'); ?></h2>
</div>

I think, I'm OK with my lang.xx.php files and my index.php. Since I'm a php beginner I'm not pretty sure about my common.php. I think there's unnecessary php code there (but everything works OK).

Any suggestions to clean this code?

Answer 1

Controller:

<?php
session_start();
header('Cache-control: private'); // IE 6 FIX

function get_lang(){
    if(!empty($_GET['lang'])) return $_GET['lang'];
    if(!empty($_SESSION['lang'])) return $_SESSION['lang'];
    if(!empty($_COOKIE['lang'])) return $_COOKIE['lang'];
    return 'en';
}

function set_lang($lang){
    setcookie("lang", $lang, time() + (3600 * 24 * 30));
    $_SESSION['lang'] = $lang;
}

function get_lang_file($lang){
    $lang_file = "languages/lang.$lang.php";
    if(file_exists($lang_file)) return $lang_file;
    if($lang_file = get_lang_file('en')) return $lang_file;
    return false;
}

//translation helper function
function l($string){
    static $translation;

    if(!isset($translation)){
        $lang = get_lang();
        $lang_file = get_lang_file($lang);
        if($lang_file) set_lang($lang);
        $translation = include $lang_file;
    }

    return $translation[$string];
}

Language file:

<?php
return array(
    'tagline_h2' => 'I create <a href="#content">websites</a>...',

View:

<div id="tagline">
    <h2><?=l('tagline_h2'); ?></h2>
    <p><?=l('tagline_p'); ?></p>
</div>

You can further improve it using OOP.