Adding modules to php

I have hacked my local php5 portfile for an rrdtool variant to add rrdtool bindings to php's modules in its ./ext directiry. But looking at the FreeBSD ports, I see that they use a separate port that uses the "USE_PHP" keyword. The docs for that option seem to imply that new PHP modules can be installed and registered with php without recompiling it, yet I don't see how this is possible. My variant works, but does anyone know if there is an alternative to recompiling php to get additional modules installed and registered into php's ./ext? Mark