I am trying to execute a PHP script at the predefined time. For instance, how can I write a php script that will force that script to be run on March 24th, 2013 at 11:14am(even if the browser is closed). I heard about cron but it is not clear to me.
Thank you for reading
Indeed cron could be an answer to your question. It is a special program that is in Linux systems and runs defined programs/commands on given time or periodically. Look here: http://unixhelp.ed.ac.uk/CGI/man-cgi?crontab+5
This would be quite troubling to do in PHP. I suggest you use something like Cron's Jobs to do this. Most cPanels have CronsJob on them, but if you don't take a look at this tutorial: http://www.thesitewizard.com/general/set-cron-job.shtml
You will have to look at what is available to you in your hosting environment. Linux/Unix with command line access? Cron is probably your answer (http://kvz.io/blog/2007/07/29/schedule-tasks-on-linux-using-crontab/). If you are using a windows server, Windows Scheduled Tasks will work (http://support.microsoft.com/kb/308569). If you have cPanel or something like it (a lot of hosting solutions use it), then you will have to check the documentation for how to schedule tasks.
I disagree with Racialz, PHP command line (CLI) is just fine for this kind of work, I have even done svn hooks in php before. The best answer for what to use can often be what you are most comfortable with.
