On non-Windows platforms, VPE is shipped as Shared Object, which is the equivalent to a Windows DLL. Therefore you can use any programming language, which is capable of calling Shared Objects (on Mac OS a Shared Object is called "dylib", but it is the same).
At the time of this writing, we do not know PHP in detail, so we can not tell you, if you can load and call a Shared Object directly from PHP. By googling for 5 minutes, I found that you can write PHP wrappers for external functions, which are called "Extensions". Maybe you need to create an extension, which in turn will call VPE. See
http://devzone.zend.com/node/view/id/1021
NOTE: We plan to release bindings for Java, PHP and Ruby within the next few months. The Java component is already under development.
Regards
Thorsten Radde
IDEAL Software GmbH