<?php
include('whatever.php');
while(true) {
    itstime();
    sleep(3600);
}
?>

<?php
$lastrun = get_last_run_time(); // get value from database or filesystem
if( time()-$lastrun > 60*60 ) {
  itstime();
  set_last_run_time(time()); // write value back to database or filesystem
}
// The rest of your page
?>