I'm pretty sure I've seen this done in a php script once, although I cant find the script. It was some script that would automatically check for updates to that script, and then replace itself if there was an update.

I don't actually need all that, I just want to be able to make my PHP script automatically run every 30 minutes to an hour, but I'd like to do it without cronjobs, if its possible.

Any suggestions? Or is it even possible?

EDIT: After reading through a possible duplicate that RC linked to, I'd like to clarify.

I'd like to do this completely without using resources outside of the PHP script. AKA no outside cronjobs that send a GET request. I'd also like to do it without keeping the script running constantly and sleeping for 30 minutes