Till Klampaeckel has published a ☞ 3 part introduction to CouchDB for PHP developers.
This is part three of a beginner series for people with a MySQL/PHP background. Apologies for the delay, this blog entry has been in draft since the 13th December of last year (2009).
While the guide is pretty good, I’m not sure why MySQL or relational databases are mentioned in the title as the references/parallels are quite rare. If you are looking for more resources on CouchDB and PHP you should also try CouchDB basics for PHP developers and Quick Guide to CouchDB and PHP.