There is a thing called java-bridge that allows you, if I understood it correctly, to talk to either java runtime or mono runtime from php. And it also provides methods of doing that the otherway around. And if I understood it correctly there are two ways the php application can access the jvm, either by socket or by using application server. The access method is configured in /etc/php.d/java.ini.
Of course to get to configure anything you have to have java-bridge installed. In my case it meant downloading the latest source, yum installing tomcat and rpmbuilding the java-bridge package from the tarball with sudo rpmbuild -tb php-java-bridge_5.4.4.2.tar.gz. Build might require some additional packages to be installed, in my case everything was already in place. Build produced four rpm-packages:
php-java-bridge-5.4.4.2-1.i386.rpm
php-java-bridge-debuginfo-5.4.4.2-1.i386.rpm
php-java-bridge-devel-5.4.4.2-1.i386.rpm
php-java-bridge-mono-5.4.4.2-1.i386.rpm
I have so far installed php-java-bridge and php-java-bridge-mono. I have also run the java-bridge examples from tomcat and found out...
Update: 02-September-2009, this entry was interrupted by something probably related to leaking dishwasher which stopped this work for whole two months.