OpenExpedio is the name for open eXtensions to PDO. It's a light-weight ORB (object-relational bridge) (also see ORM). It implements the very simple, but effective, Active Record pattern for data access. The library works on PHP 4 (xPDO 1.0 only) and 5, and takes advantage of the newly adopted standard for database persistence in PHP 5.1+.
Documentation on xPDO can be found here:
More information about xPDO can be found at the xPDO website.