Running a certain PHP function at specified intervals!

I had posted this question some time back fellas ... please let me know about the same. I didn't get any kind of reply for this and the necessity is rather dire! Please let me know about any kind of solutions for the same. Dear All, How can I make a certain php function run at SPECIFIED INTERVALS on Windows 95 / 98 / NT machines or maybe on Linux / UNIX as well? It's something like, running a daemon or a service but what language should I use to connect to PHP function and call it at the specified intervals? Doesn't the web-server (APACHE) run like a daemon / service itself? So then, is there a certain configuration setting in the config. file to specify what function we want to be run at the given intervals? Basically, I want a PHP function to be launched at given interval without the user's (admin's) intervention, that would perform the required checks in the database and update the entries, corresponding to the found ones. Please let me know about the small piece of code as well that can help me understand it better ... if possible! Thanx -Romi