An open source PHP-based OpenID identity provider using LDAP as
backend.

OpenID-LDAP is a small, fairly lightweight, standalone, multi user
Identity Provider for OpenID authentication.  It comprises a few PHP
scripts that can be used by one individual to run their own personal
OpenID IdP.

This program requires no external libraries, and has very minimal
requirements.  It should run on any PHP server (v4.2+), and can
support OpenID in 'Smart Mode.'  This program caches all data using
built-in PHP session handling, so it requires no database, and no
explicit write access to the file system.

OpenID-LDAP is NOT compatible with Suhosin or other hardened PHP
systems.

WWW: http://www.openid-ldap.org/