I've tried integrating sfPHPOpenIdPlugin but that hit a dead-end since it's built for Symfony 1.2 and relies on deprecated PHP functionality; I also had a go with sfGoogleLoginPlugin which did authenticate correctly but lacks extended capability to retrieve user details (+ would restrict me to Google; obviously).
I'm thinking the most viable solution is to link in one of the various PHP libraries available into my model.
I'm wondering if anyone else has had any success/tips with such an integration and what libraries to consider?
Update:
Having gone off this as a concept I switched to using sfTwitterAuthPlugin for my portfolio and any Symfony-based web apps I build.
For anyone interested, the version on the official plugins website lacks some useful functionality, I'm actively maintaining improvements at https://github.com/stevelacey/sfTwitterAuthPlugin.
Actually sfPHPOpenIdPlugin was updated yesterday and is compatible with Symfony 1.4.