Timothy Boronczyk has posted a class that provides a different sort of theory on database access:

I was thinking today about database APIs when inspiration struck. I ended up hacking out the following class, which I think demonstrates a rather interesting approach to interfacing with a database (interesting enough at least to post here).

His class implements an Iterator and lets you bend a few of the rules PHP normally has in place (use of the magic methods, special characters in an identifier). He also includes an example of its use - connecting to the database, selecting information and pulling that information back out.