PHP: language system - json2Array

gistfile1.php

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


function showUrl($lang){
  $url = basename($_SERVER['REQUEST_URI']);
  if(isset($_GET['page'])){
    $url = "?page=".$_GET['page'];
    $url .="&lang=".$lang;
  return $url;
  }
  else
    return "?lang=".$lang;
}


if(isset($_GET['lang'])) {
  $lang = $_GET['lang'];
  // register the session and set the cookie
  $_SESSION['lang'] = $lang;

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

$str = file_get_contents("languages/lang_{$lang}.txt");
$lang = json_decode($str,assoc);