A problem with Sessions: Developing and App inside PostNuke

Hi to all, I'm developing different applications using PHP and MySQL within PNuke, because PN API is very complex and I didn't have time to deeply study it I decide the best aproach to my application, was to create an independent user (from that in PN member), with it's own session and login method, so I developed such a system and it works outside PostNuke, but because PN creates their own sessions, when I add PN header and footer, and try to execute my app I got "Warning: Cannot Session cookie - headers already sent by ... and Warning: Cannot send Session cache limiter - headers already sent ...", I understand this happened because this is within PN there are already headers sent and that's why when I call my session I got this error message, so my question is if there is a way to overcome this ? Regards, Rick AXIS Computers