PHP (or any language for that matter) can just as easily be used as a daemon as on the web. This can be especially useful when solving problems that can't "complete" in less than 500 ms which one shoots for on the web. As you write an application to handle things such as those mentioned below, be sensitive to the processing, disk space, and time needed to process these requests in planning how to handle these. As an example jobs of a small size might be handled inline by the code that handles the form submission, but for larger jobs it queues them for background processing.

great for background/async processing of:

  • photos
  • movies
  • reports
  • imports of data


  • use the same codebase as your app
  • use the same expertise on your team of programmers


  • signals
  • one thread
  • memory (this will have to be a whole separate article)
  • starting and stopping

A typical Daemon class I use:

abstract class Daemon {
    protected $done = false;

    public function __construct($argv) {
    public function init() {
        pnctl_signal(SIGTERM, array($this, "onSignal"));
        pnctl_signal(SIGINT, array($this, "onSignal"));

    abstract public function run();
    public function shutdown() {}
    public function isDone() {
        return $this->done;
    public onSignal($signal){
        switch ($signal) {
             case SIGTERM:
             case SIGINT:
                $this->done = true;
                 // handle all other signals

As you can see, we've started to tackle some of the challenges here. The idea is to handle signals, specifically I usually care about SIGTERM (default when using 'kill' on *nix) and SIGINT (from pressing Ctrl-C). Both will cause the program to exit gracefully.

I'll be posting the class I use to run Daemon's tomorrow.