Session variables unset between page content changes
<p>i am using 1 index.php page and using navigation links to send values $_GET values which are used to retrieve page content from mysql database to effectively change the page which is working fine.
On one of the nav links a session variable is set when clicked which i want to use later, but when i click another nav link that doesnt set sessions the previously set session has been unset and so has no value. i have checked the session_id which is the same on each page and have checked that the session variable is actually being set by outputing to the screen, it just disappears when a new page is clicked.</p>

<p>Thanks</p>
