Finally a couple of words about integration into Model-View-Controller applications: such Zend Framework applications are implemented using the Zend_Controller class and they use objects of the Zend_Controller_Response_Http class to prepare HTTP responses and send them back to the user's web browser.

Zend_OpenId_Consumer doesn't provide any GUI capabilities but it performs HTTP redirections on success of Zend_OpenId_Consumer::login and Zend_OpenId_Consumer::check. These redirections may work incorrectly or not at all if some data was already sent to the web browser. To properly perform HTTP redirection in MVC code the real Zend_Controller_Response_Http should be sent to Zend_OpenId_Consumer::login or Zend_OpenId_Consumer::check as the last argument.