I have wrote this following piece of code that shows how to work with global sessions (global to all clients) and private sessions (private per browser instance i.e. session cookie).
This code is usefull to store some read-only complex configuration and store it once (per server) and save the performance penatly for doing the same thing over each new private session...
Enjoy:
<?php
// Get the private context
session_name('Private');
session_start();
$private_id = session_id();
$b = $_SESSION['pr_key'];
session_write_close();
// Get the global context
session_name('Global');
session_id('TEST');
session_start();
$a = $_SESSION['key'];
session_write_close();
// Work & modify the global & private context (be ware of changing the global context!)
?>
<html>
<body>
<h1>Test 2: Global Count is: <?=++$a?></h1>
<h1>Test 2: Your Count is: <?=++$b?></h1>
<h1>Private ID is <?=$private_id?></h1>
<h1>Gloabl ID is <?=session_id()?></h1>
<pre>
<?php print_r($_SESSION); ?>
</pre>
</body>
</html>
<?php
// Store it back
session_name('Private');
session_id($private_id);
session_start();
$_SESSION['pr_key'] = $b;
session_write_close();
session_name('Global');
session_id('TEST');
session_start();
$_SESSION['key']=$a;
session_write_close();
?>
[EDIT BY danbrown AT php DOT net: Contains a bugfix provided by (lveillette AT silexmultimedia DOT com) on 19-NOV-09.]