I have a video sharing site and it would be problematic to use a XML for all videos within the site to load up the recommended videos for the Viral Plugin.
Is there a way to use a PHP file instead to write out XML content to the player to use?
If yes is there any example of how to do this?

http://www.longtailvideo.com/jw/?search=playlist+generators
Adapt one of the playlist generators to output the correct XML for the viral plugin recommendations.