Currently I have a database of users. I have a PHP script that checks each user to see what kinds of reminders I should send them each day. However, as users increase, my script execution will doubtlessly increase. I want to prevent it from hanging, and to see its progress. How can I split up this problem into multiple cron jobs that happen throughout the day, or some other way? If this is not the way that people normally do mass emails to users, then what is the usual way?

Thanks so much.

Why do you need a cron job?

Just have a script that runs when a page is opened, checks a maintenance task database, runs the next task then flags it as complete.