On the Content with Style blog there's a new post looking at creating a worker process with PHP and the help of two other tools - Beanstalkd and Daemontools.

Sometimes things just get too heavy for a straight forward approach. Memory usage might be too high or interaction might be delayed. In this case it might make sense to queue the task up for later execution.

The technique uses beanstalkd as a messaging queue to handle the requests based on the user's request via the interface the beanstalkd library provides. Then, to keep the queue running in the background and available, he uses daemotools to run a worker process. You can download the complete code for a working example.