I’ve been working on [size=“4”]ActiveDocument[/size] for awhile, which is an ORM similar to CActiveRecord, but for documents.
ActiveDocument currently has 3 drivers, supporting Riak, MongoDB, and Memory (PHP in-memory objects)
We’re currently using ActiveDocument within our own apps (first with Riak, later we switched to Mongo), and it suits our needs for the most part. There are some areas where it still needs development, but currently it’s quite functional as-is.
There is already another Yii user developing a Riak application using the extension, it would be nice to gain more users.
If anyone would like to try out ActiveDocument, whether for actual development or just to help out, that would be greatly appreciated.
I need others using this extension, to poke holes at it, find flaws, needed features, etc.
Also, if anyone is adept with writing tests, it would be great to get a test suite started for ActiveDocument, since it already has 3 different drivers and will hopefully have at least 2-3 more in the next few months.
Anything anyone can do to help would be greatly appreciated.
I recommend using the latest commits from the repo, ideally from a clone.
Some initial notes on install/configuration
Clone from Bitbucket (hg):
hg clone https://bitbucket.org/intel352/activedocument
Clone from Github (git):
git clone git://github.com/intel352/ActiveDocument.git
Any questions, please do ask 
You can also message me or email me
[size="4"]Some example usage:[/size]
Example showing relations, nested documents, custom primary key, etc
Running a custom map phase against a Riak cluster