On the SitePoint PHP blog today, Harry Fuecks talks about some of the options to integrate PHP with Java - the Caucho updates specifically.

From this post on the server side it seems Caucho have added PHP support to their Resin Java App server.

There are a number ways to integrate with Java, by which I mean PHP-the C version.

What's interesting about what Caucho seem to have done is, rather than integrate with PHP-C, they've written their own parser for PHP scripts in Java, from which they generate Java byte code for execution. I say "seem" because I've only glanced at the source and found a convincing-looking PHP parser in there. He also points out a wiki entry with some more information on it...