1 thing I noticed when starting to create skills is the lack of PHP SDK (or that I could find anyway). So I decided to start my own.
Over the last couple of days I have started work on the SDK. Although it is currently a long way off things are shaping up nicely.
If you are interested in using the SDK you can find it over on Github. In the repository you will find an examples folder. This has some useful examples to help get you started.