Hey,
Something you might want to try is to call the PHP by itself with a known good flv file passed to it in the query string. This way you can see if the video is being added to the XML output. That was one of the issues I had, for some reason it wouldn't ouput the path to the FLV file. The other issue I was running into was my lack of knowledge in PHP 5.X. I'm a .NET programmer by day and a PHP hack by night so I'm a little behind on the PHP framework for XML...

Dapanther