On his blog, Vinu Thomas has posted a guide to installing the Java bridge for PHP on an Ubuntu system:

If you're looking for the easiest way to install the PHP Java Bridge in Ubuntu, follow these simple steps...

The basic steps are quick and easy - be sure you have Java installed on your system (commands to install are included), download the Java bridge from Sourceforge and issue the commands (again, included) to install it into your apache2 package.