On the Zend Developer Zone there's a new post talking about scheduling in applications ("scheduling elePHPants") including both library recommendations and advice about code reuse.

It was while I was creating the 100th or so cronjob to do some very similar to the other 99 that I thought, “Hey! Why not just put all this in a database and check it once a minute instead?” [...] It would be so much easier to deal with in PHP. Also, cron does not scale well at all either in performance or management.

The problem is that cron is an elegant solution for “Do this at that time” type of problems. Every solution I came up with was basically re-creating cron. That in itself isn’t a bad thing, but the logic involved in doing what cron does is mind-melting.

[...] Then it hit me, I am probably not the first person that has had this need. There have probably been other people who needed to implement “Do this at that time” within a PHP application. So I started looking around. What I found was encouraging.

The author then mentions several packages that he went through searching for the right solution to his problem, noting that while Laravel-based solutions seemed nice, they wouldn't work with his framework choice (Slim). He decided on the cron-expression package, finding it to be the best fit for the project's needs.

I had spent countless hours trying to create the solution myself. [...] I got so lost in solving the problem, I forgot to look to see if someone had already solved it. [...] After I finally came to my senses, I tweeted that out to remind myself to “Use the Source”.