Suppose i Am having some piece of code and i want it to be executed after every 24 hours automatically .
No ideas how to implement it 
That’s a very good question, and I am wondering either. I searched through Google and some IT guys recommend crontab – a unix, solaris utility that allows tasks to be automatically run in the background at regular intervals by the cron daemon.
And I don’t think a single .php file can execute its own given regular intervals without invoking it. So I think crontab is the auto-launcher…
That was a cool reply as well .BUt in future if i suppose to put my code online on a web server what can i do then ?
PHP only execute when someone calling them, if not posible make a php auto execute.
For this, the solution will be an external program that execute php file.
In Unix it’s to easy, use crontab because you can select the time and user that execute the file.
In another SO, you can use other scheduling to execute.
Okay,i have modified my thots and i now want that a user should click the link only ONCE in 24 hours .
How can it be done?