Using Googles SSO for GApps

Hi, I was wondering if anyone has set up SSO using googles api for apps. http://code.google.com/apis/apps/sso/saml_reference_implementation.html is their implementation guide but I was wondering if anyone has done it, and if I could have a peak at the code you used, mainly for the encrypting of the information being sent, also for the generation of the xml. I have done some googling and can find a few java implementaions, but no php ones - maybe I cant search so if there are some examples around please excuse my ignorance. Thanks in advance, Ian