PHP session var strange value through AJAX

[O_Dog]

my code is a bit messy so I'll try to explain to you in words:I have this index.php page that shows a random file from my files table in my database. People have the opportunity to rate these files by clicking on notes that open "vote.php" through a small AJAX pop-up.Now here's the problem. On index.php I pull the ID from the database and output it:\[code\]$_SESSION['file_id'] = $file_id;echo $_SESSION['file_id'];\[/code\]But when I open the vote.php pop-up and write:\[code\]session_start();echo "SID="; echo $_SESSION['file_id'];\[/code\]The value is not the same! What could cause this?Thank you very much.