Running an Automatic PhP Script

  First if your server is linux they should have cron jobs unless they restrict that to thier clients wich will make them a bad hosting company, and if your working with a windows host it use a library called scheduale task, now a good hosting company, would give you any of the options to set things up on their control panel, try finding a hosting provider that gives you cpanel for linux server wich is easy to set up a cronjob, the only way you can accomplish runing a script the way you want is that your hosting provides you with those functions.

In the worse case you can get the service with other companys like www.cronjobs.org/ wich will call you file script and execute it giving the correct url of it on your host.