Chris Ravensroft has posted a quick guide to getting the Java-related web server, Tomcat, up and working with a PHP installation.
Sometimes, you want to run PHP with Tomcat. Why? Well, you may have a legacy product, for instance, that will require servlets for many more years. Or you may be using this gigantic Java program and are only interested in adding a tiny PHP piece on the side.
It's a pretty simple process and most of the steps are the standard "download, install, unpack" sorts of things. The important things are the web.xml document you create and the additions to the servlet.properties file to make the PHP module work.