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Egidestr. 9
44892 Bochum


Random thoughts, bright ideas and interesting experiments. In short the ramblings of a fulltime nerd.


Periodic - A PHP based cron utillity

Jakob Westhoff

Periodic is a fully unit tested PHP based task runner. It is supposed to deliver a basic implementation for managing all kinds of recurring tasks and events inside your web application. It has been designed with having all kinds of different web hosting environments in mind. It is capable of running on most shared hosting systems as well as root servers.


Kore and me needed some kind of recurring task management system for different projects we are currently working on. I started working on some kind of CronjobIterator which is capable to parse a cron definition -- you might know this definitions from the famous vixieccron daemon -- and provide an iterable list of timestamps matching this definition. The vcron definition syntax seems to be the most intuitive and widely spread syntax to describe recurring events, therefore we chose it.

As Kore got to the point where he needed something like this in arbit he wrote a design document for it and started discussing it with me. We tried to create a modular and flexible system fulfilling the needs of both our projects. I think we did a good job with that. I finished the CronjobIterator while Kore began writing other base components of it. In the next weeks I am going to implement the cron daemon part of it which will handle forking and parallel grouped task execution.

If you want to take a look at this nifty little tool, you can check out its subversion repository at:


Question about vixie-cron

I have one personal question to you. During my readings of the vixie-cron man pages to figure out the exact syntax definition of events, it came to my attention, that the month field allows the number 0-12. If you know what the 0 month in this case is, I would be glad if you could just tell me using the comment function of the blog or sending me a mail. Thanks :).