Which MongoDB library to use for a stand-alone PHP project with Symfony?

I am leading a new project where we're convinced that MongoDB is the right choice for database. We have decided that the architecture would be SOA, so the web part will be developed using Symfony and the service part will be developed using light-weight REST framework Tonic.

Now, in the service part, we'll be communicating with MongoDB and for that, we have looked into a number of available MongoDB libraries: Doctrine MongoDB ODM, Mondango, ActiveMongo, MongoRecord, etc. However, we are not sure which one to pick.

I was wondering if anyone can share their experience with these libraries so that we can make the right choice. Here are some of the properties we consider the library should have:

1. Plain PHP classes for defining documents (instead of array/config files)
2. Support for references
3. Efficiency in operations
4. Easy to understand API

Personally I would go with Doctrine2 ODM. Seen as you have already decided on Symfony as your framework for doing the heavy lifting the pair are well aligned as far as I understand. You should be able to use this https://github.com/doctrine/DoctrineMongoDBBundle to integrate the two pretty quickly.

The doctrine setup ticks all the boxes you've set for your project goals and is fairly easy to get working with. Most importantly, it's an active project so bug fixes/features/documentation updates happen fairly regularly.

We use a similar setup, except zend framework instead of Symfony, and we're very happy with the results.

Hope this helps.