Sag is a great PHP library for CouchDB created by Sam Bisbee. Sag's guiding principle is simplicity, creating a powerful interface with little overhead that can be easily integrated with any application structure. It does not force your application to use a framework, special classes for documents, or ORM, but you still can if you want to. Sag accepts the basic PHP data structures (objects, strings, and so on) and returns either raw JSON or the response and the HTTP information in an object.
I'll walk you through installation and the basics of Sag's functionality, but you can also visit Sag's website at: http://www.saggingcouch.com/ for examples and documentation.