On the Zend Developer Zone today Michael Bailey has posted an introduction to CouchDb including some sample code (in a download) and a look at the basics of using the database itself.
I will not detail the installation of the CouchDB server, the wiki got enough details. For the rest of this article I will assume that we have a running CouchDB server waiting for our queries on couch.example.com on port 5984 (the default CouchDB port). Setting up PHP on Couch is not really complicated : just download it on github.com, extract the archive : the interesting bits are in the lib folder.
He starts with some of the key terms you'll need on the CouchDb side (like JSON, documents, _id and _rev) followed by the interaction between PHP and the database - creating a database, storing a document, using the document object mapper and working with views.