Shortly Silverlight is a cross-browser platform that can be used for developing client-side components that run in the web browser and contain rich media, graphics and can interactively communicate with the user. The language that can be used for writing Silverlight code can be in general any .NET language, so our goal is to allow using PHP by making Phalanger compatible with Silverlight.
He has two demo applications - a simple car app and a helicopter game - he uses as examples. He focuses on the simpler of the two, the car demo, and gives the XAML source, the code for the PHPX file and talks some about the method of deployment that'd need to be used to get the app out to others.
You can download the complete source for the examples (including the Phalanger Silverlight runtime) as well.