Run a PHP page on the server after time periods automatically -

i have php page read , write data in database. there way can run php page on server automatically (not request of client) every n seconds?

rather having cronjob, might easier/more efficient have 'daemon' style script.

a script running, , @ set intervals.

<?php     while(true) {         do_stuff();         sleep(30);     }

(more efficent, because script doesn't need full start every time it's run. can hold configuration etc, between calls do_stuff.)

of course 'do_stuff()' might calling script

function do_stuff() {     file_get_contents('http://example.com/scripts/calc.php'); }

Three