cron - Is it possible to make a PHP script run itself every hour or so without the use of a cronjob? -

I'm pretty sure that I've done it once in php script, though I can not find the script. It was a script that would automatically check the update of that script, and then an update would replace itself.

I really do not need it, I just want to be able to make my PHP script automatically runs every 30 minutes an hour, but I want to do it without chronboos, if possible .

Any suggestions? Or is it even possible?

Edit: After reading an potential duplicate associated with RC, I want to clarify.

I want to do it completely without using resources outside the PHP script. Any chronobogs outside the aka who send GET requests. I want to run this script continuously and without sleeping for 30 minutes

If you will do this Get enough hits ...

Store a last updated timeline (file, db, etc ...) anywhere. In the file that gets enough hits, it adds the code which was last updated xx minutes ago. If this was then run the script.