Just curious, but is there a particular reason you don't want to use a cron job? Using php for maintenance without user interaction might be tricky since usually it only runs when a user is accessing the site. however if their is a significant reason that you dont want to or can't use a cron job then I can see why it'd be worth looking into.
There're cases where we run windows server, which doesn't have cron job. I would always use cron job on linux machine. Some hosting might not provide access to cron job.