Building OpenID providers is much less common than building
OpenID-enabled sites, so this manual doesn't cover all
Zend_OpenId_Provider features exhaustively, as was done for
Zend_OpenId_Consumer.
To summamize, Zend_OpenId_Provider contains:
A set of methods to build an end-user GUI that allows users to register and manage their trusted sites and profiles
An abstract storage layer to store information about users, their sites and their profiles. It also stores associations between the provider and OpenID-enabled sites. This layer is very similar to that of the
Zend_OpenId_Consumerclass. It also uses file storage by default, but may used with another backend.An abstract user-association layer that may associate a user's web browser with a logged-in identity
The Zend_OpenId_Provider class doesn't attempt to cover all
possible features that can be implemented by OpenID servers, e.g. digital
certificates, but it can be extended easily using
Zend_OpenId_Extensions or by standard object-oriented extension.