Description:
------------
After calling session_start() generates two session files, $_SESSION variable is strored in which SID is forgotten. 

Reproduce code:
---------------
<?php 
session_start();
echo 'SID:'.session_id();

 $_SESSION['a'] = 3;?>
<p>look on <a href="another_page.php">next</a></p>

another_page.php
---
<?php 
session_start();
if (isset($_SESSION['a'])){
	echo 'Session var a = ',$_SESSION['a'].'<br />';
}else { 
echo 'Session is not registered.<br />';}
echo 'SID:'.session_id(); ?>

Expected result:
----------------
SID:gahug37g6ga2e4qjuoo8988d62
look on next

----
Session is not registered.
SID:5elroalaf46hc4muhle5c18896