Domain-driven design with Zend
There is a newsgroup formed by Matthias Verraes about doing DDD in PHP, mainly with Sf2.
Somewhat older is a series of articles by Federico Cargnelutti on how to do DDD with PHP and in parts with ZF that might be of interest to you:
- Domain-Driven Design and MVC Architectures
- Domain-Driven Design: Data Access Strategies
- Domain-Driven Design: The Repository
- Domain-Driven Design: Sample Application
Regarding ZF, there has been a proposal for Zend_Entity and Zend_DataMapper for some time, but development on those has been terminated in favor of integrating ZF with Doctrine. Doctrine is also the closest thing to Hibernate in PHP.
When googling for DDD with PHP, there will be a few additional resources, but nothing as comprehensive as the resources available at the official DDD site with code for the App described in Eric Evan's DDD book.
Have a look at my project at GitHub. It tried to follow the principles of DDD, SOLID and OOP.PHP and DDD. There is no ORM inside but a hand-made Data Access Layer. Domain entities exchange messages. Presentation Layer gets a special kind of objects. You will find a lot of factories. They are intended to simplify unit testing and maintenace. I hope some techniques can be of interest for you.