Rather than calling the script via a url (which would then probably be accessible to the world via your webserver) you probably want to compile a standalone php binary. There are linux packages for this (do a google search for "arvin php rpm"). Or you can always compile from source. You can change a few of the options to make the standalone binary a little more secure, and then drop it in /bin or /usr/bin.
Then, you can write shell scripts using /usr/bin/php instead of /bin/sh or /bin/bash, etc. Just be sure to chmod them executable.
Lacey