Thanks to Penny for informing me of the misguided link in the linksystem. The bug has been squashed and the fix is now available for download.
DevShed have an article by icarus called Database Abstraction With PHP. As the name suggests it looks at PHP's Database Abstraction Layer. Simply put it the database abstraction layer make it possible to write generic code that can be used to access different types of database without have to re-write the code.