I'm experiencing a strange issue with the PHP session. I can store values and everything until the end of the request. As soon as a new request is created, a new session file is created with a new session and data loss of the previous session as a result.
I have installed both php and apache manually on a Windows 7 machine. The session.save_path setting is set to null, but the files are being written to: C:\Windows\Temp. The session files are present there and have the actual values in them so I don't think that this is a permission issue.
Note that session_start() is being called at the very start of the php file that handles the request. This is not a code issue as I have used dummy code to verify the behavior on a different machine with a xampp server. There everything works fine.