Ivo Jansch has a recent post made the other day that takes a look at one of the recent offerings from IBM targeted at PHP developers - the functionality to allow PHP to run on their System i platform.

Some of the developers at Ibuildings are working with PHP on IBM's System-i platform. If that name doesn't ring a bell, it has been called 'iSeries' for a while and it's basically a new name for the old AS/400. [...] Recently IBM and Zend have teamed up to port PHP to the i5/OS operating system. So far this port seems succesful; one of the reasons is perhaps that PHP is easier to adopt by traditional System-i developers than Java, which forces you to learn Object Oriented Programming.

He makes mention of the db2 database extension you can use to access the database as well as a "i5 toolkit" to help with the same. He even links to an article talking about it.