How does PHP interact when using Java?

Hi, I've just got PHP working with Java. It connects to a remote Oracle DB with Java and without the Oracle Client installed on my machine, it's sure a beauty. What I was wondering, what's behind it, I mean how does it work? I transfer Objects in Java and get data out. How do PHP and Java interact, after all they are two different technologies. I've searched google and pretty much every site I could think off, but I've found nothing more than a setup tutorial. By the way, I should mention if you have them interact, Apache + PHP doesn't like java packages at all. PHP blows off with a severe error message. thx Jan Bro