Ross Tuck has submitted a new article he's posted about persisting value objects in the popular PHP database storage and object mapping library, Doctrine. Value objects are immutable objects that " follow value semantics rather than reference semantics".
I’ve been using more and more Value Objects in my applications over the last year, primarily with Doctrine ORM. Value Objects are an extremely powerful technique and I’ve been impressed with how much they can clean up a codebase. One of the main questions I’ve had when starting with Value Objects is how to persist them with Doctrine. This post attempts to create a reference for all the different persistence techniques I’ve seen so far.
You'll need to be familiar with Value Objects and Doctrine before starting (it's not an "intro to Doctrine" article). His example sets up an "IPRange" and an "IPAddress" that are stored in a "Server" instance. He talks about mapping the value object to the database and the getter/setter to do the work. He also touches on DBAL types, working with multiple columns in the entity and the "promised land" of embeddables. He finishes off the post looking at collections of entities and some of the other options to what he's shown (including serialization).