So as far as I can tell this isn't really possible the way I was hoping. The 2 solutions I can use are setting an outside variable (in the DB or flat file) and checking for it periodically, or since this is actually listening for a UDP broadcast I can just send out a UDP with the information I would like to pass to the script. While neither of these are particularly elegant, they both work.
On a side note, don't build UDP servers in PHP. This was really just a proof of concept, but is horribly inefficient. While using php to handle the data in the broadcast seems to work well, it is definitely preferable to use Python or Java for the listener itself and pass the data to a script.