Is there a good object-relational-mapping library for PHP?
I know of PDO/ADO, but they seem to only provide abstraction of differences between database vendors not an actual mapping between the domain model and the relational model. I'm looking for a PHP library that functions similarly to the way Hibernate does for Java and NHibernate does for .NET.
Look into Doctrine.
Also, check out Xyster. It's based on the Data Mapper pattern.
Also, take a look at DataMapper vs. Active Record.