Mastering PHP 7

The chain of responsibility pattern

The chain of responsibility pattern allows us to chain code in a sender-receiver manner, while the two are decoupled from each other. This makes it possible to have more than one object handle incoming requests.

The following example demonstrates a possible chain of responsibility pattern implementation using the logger functionality as an example:

<?phpabstract class Logger{    private $logNext = null;    public function logNext(Logger $logger)    {        $this->logNext = $logger;        return $this->logNext;    }    final public function push($message)    {        $this->log($message);        if ($this->logNext !== null) {            $this->logNext->push($message);        }    }    abstract protected function log($message);}class SystemLogger extends Logger{    public function ...