There is a special group of applications that require a different PHP script execution model. [...] All of [these special] applications need to be run in the background as daemons - something that PHP was never designed/supposed to be good at. The plain C language is a weapon of choice when it comes to writing a daemon implementation, but then again, if the application in question does not depend on high performance and concurrency - PHP can do the job quite well.

He talks about using the command line interface to run the scripts, creating the while loop to keep execution going and creating the non-blocking socket so that the script can accept new client connections. He also mentions using upstart to run the script in the background and the proctitle PECL extension to give the process a custom name in the process list. He also touches on log files and forking/parallel processing.