Most of the work that I've put into the project has been research and databasing, so the PHP I've written isn't so extensive that it would be incredibly hard to rewrite, and most of it will need revision as I try to incorporate it into a larger system.
Perl is more dynamic than the PHP that's locked up in my server and from what I've read can probably be integrated more easily into other systems. This might actually become more of an issue later if I work with systemic grammars. Perl modules will allow me to cut some corners, and I'm all for that. I already see that there are some modules that do almost exactly what my stuff does. Lastly, although it at first didn't seem like much of a factor, the Perl community is more centralized and geared towards this type of work. I found very little documentation on NPL+PHP, because that's just not what PHP is about.