The Zend Developer Zone has gone IBM crazy with three different posts concerning the blending of the PHP language with the i5/OS platform - specifically the use of DB2, a free book that's been published, and a real code example to get you started.
First off, the book - "Developing PHP Applications for IBM Data Servers". Cal talks about its contents, including a brief description and a listing of te chapters. Topics covered include the installation and configuration, wokring with DB2/Informix, and an introduction to Service Data Objects for PHP.
Next up is Cal's announcement of the official melding of DB2 and PHP on the i5/OS platform. He points to a tutorial ("Use PHP scripts to access DB2 UDB for iSeries data with Zend Core for i5/OS") for an example of these connections.
Finally, Cal wraps it all up with another example from the Zend site that "illustrates features and functions using the db2 extensions in the Zend Core for i5/OS PHP engine".