DJJob is our database-backed job system that allows PHP web applications to process long-running tasks asynchronously. It is a nearly direct port of delayed_job, one of the most popular Ruby/Rails job processing systems.
A few months ago, I went searching for a PHP-friendly equivalent of the many popular queue/worker-based job systems available to Ruby apps. But the best I could find was a few pointers to pcntl_fork. There are a few language agnostic-systems, but in general they seem more complicated and often rely on additional moving parts.
Delayed_job's design is attractive because most people are already running a SQL db, and storing jobs in the db instantly buys you a pretty full featured job management system in phpMyAdmin.
The result is that we decided to port delayed_job to PHP and bring simple, robust job processing to PHP web apps.
Take a look at the github repo to see how to use it and to get the code.