There’s a short note on the PhpGedView site about plug-in modules:
PhpVedView version 3.3 supports a new modular interface so that other programs can be plugged into it more easily.
There are currently two modules available for PGV, the ResearchLog and a punBB bulletin board. No new functionality has been added to the ResearchLog since its last release. But with the new modular interface it will be easier to keep it up to date and add new features, so keep an eye out.