I had some "fun" today trying to get PDO connecting to Microsoft SQL Server. This turned out to be more of an effort than one would think, while at the same time it proved to be rather simple once I learned the secret. The hard part is finding the right information online - there is a LOT of outdated information out there. Here's the secret...
I was using a Ubuntu 9.04 installation, but the following *should* be enough to get you moving in the rigt direction for other distributions.