You don't really need to compile the PHP script. Even if you did compile the script into an EXE, you would still need a scheduler to run it at the desired times.
What you really need is a scheduler to start the script at the desired times. Examples of schedulers would include cron, Techscheduler, (WindowsNT) AT-command, and so on.
-- Michael
Darkstreak Consulting
www.darkstreak.com