For me, the easiest is to just write everything inside the ubb framework. The authentication is done for me, and everything that has to be displayed is done for me.
Look at /scripts/sample.inc.php for an example on how to do this.
Donate to UBBDev today to help aid in Operational, Server and Script Maintenance, and Development costs.
Please also see our parent organization VNC Web Services if you're in the need of a new UBB.threads Install or Upgrade, Site/Server Migrations, or Security and Coding Services.