In most cases hosting panels has CRON jobs available, so using cron is not an issue. Just sometimes you do not want to bother with it because of many reasons like no cpanel password, makes your script installation process complicated, or even cron is simply not available at all.
In this case I found interesting technique how to overcome this.
The idea is simple and is borrowed from official documentation comments. In PHP it is possible to sent browser output and continue to execute other PHP code.
This means that on each page request, PHP generates full HTML, sends to the user and closes the connection. User is happy to view the page, however on the server PHP script may execute useful stuff.
Code looks like this:
// Generage HTML page here
// All magic goes here
$output = ob_get_clean();
echo $output.str_repeat(' ', 10000) ."\n\n\n";
// Now page is sent and it safe to do all needed stuff here
If you need to run CRON jobs continuously and not to depend on the user visits, you may initiate a SELF request to the same page using CURL after all tasks are done.
Based on this technique very easy to make a full CRON class which will handle all the dirty job, may be in future )