David Coallier has posted about a database abstraction layer that he's been developing for PHP 5.2.x only systems and wants some opinions on his methods:

I made a very light DBAL that uses PHP5.2.x only (Since many people seem to want that) and it has the exact same DSN syntax as MDB2 for now and the query method are also called the same (No API Changes). [...] The main goal of the DBAL is to have a very effective and light way of switching RDBMS but also the possibility to change your DBAL to something more "0feature complete" as such as MDB2.

He includes the list of query method names and the types of databases that he wants it to support (as well as mentioning the fact that it would be unit tested for reliability).