As of March 2008, the OpenSSO PHP Extension (formerly known as 'Lightbulb') is 
deprecated in favor of simpleSAMLphp - see http://rnd.feide.no/simplesamlphp.

simpleSAMLphp builds on the concepts first explored in the OpenSSO Extension to 
offer a full SP and IdP implementation of SAML 2.0 and Shibboleth 1.3.