PHP language selection - php

Question

I have two flags, where you can click on to change the language.
But the weird thing is, it works but I have to click twice to stay in the language. (The session variable dissapears too if I go to a other page)
Like if I click one time on the flag, it doesn't stay with the session variable.
<?php
if(!isset($_SESSION['lang']))
{
$_SESSION['lang'] = "NL";
}
if($_SESSION['lang'] === "EN")
{
?>
<div class="language-selector">
<a href="page.php?id=1&lang=NL">
<img src="img/nlnon.png" onmouseover="this.src='img/nlact.png'" onmouseout="this.src='img/nlnon.png'"/>
</a>
<a href="page.php?id=1&lang=EN">
<img src="img/enact.png" onmouseover="this.src='img/enact.png'" onmouseout="this.src='img/enact.png'"/>
</a>
</div>
<?php
}
if($_SESSION['lang'] === "NL")
{
?>
<div class="language-selector">
<a href="page.php?id=1&lang=NL">
<img src="img/nlact.png" onmouseover="this.src='img/nlact.png'" onmouseout="this.src='img/nlact.png'"/>
</a>
<a href="page.php?id=1&lang=EN">
<img src="img/ennon.png" onmouseover="this.src='img/enact.png'" onmouseout="this.src='img/ennon.png'"/>
</a>
</div>
<?php
}
?>
This is the code to show the correct language for each page (only one right now)
<?php if($page_id == 1){
if(isset($_GET['lang']))
{
$language = $_GET['lang'];
if($language == "EN")
{
$_SESSION['lang'] = "EN";
include('includes/EN/onskantoorEN.php');
}
else
{
$_SESSION['lang'] = "NL";
include('includes/NL/onskantoorNL.php');
}
}
else
{
$_SESSION['lang'] = "NL";
include('includes/NL/onskantoorNL.php');
}
?>
To sum it up:
I want to click on <img src="img/nlnon.png>
or <img src="img/nlennon.png>
and let it immediately show the correct language, instead of clicking it twice.
I've wrapped the session variable around the link, so I'm not sure what's going wrong.

Answer 1

From your comments your first snippet is executing before you properly assign your session.
Try including header.php file after code where you evaluate and assign the language in session variables.
You can also include the code for initializing proper session variable for language in header.php file. Just make sure it gets executed first.

Answer 2

I think the second code snippet should be like this:
<?php
if ($page_id == 1) {
if (isset($_GET['lang'])) {
$language = $_GET['lang'];
$_SESSION['lang'] = $language; // todo: validate the GET parameter
} else {
$language = $_SESSION['lang'];
}
if ($language == "EN") {
include('includes/EN/onskantoorEN.php');
} else {
$_SESSION['lang'] = "NL";
include('includes/NL/onskantoorNL.php');
}
}
?>