Chain of Responsibility pattern PHP code example

ChainOfResponsibility.php

<?php

class Job {
  private $details;

  public function __construct($details) {
    $this->details = $details;
  }

  public function requirements() {
    return $this->details;
  }
}

class StackDetector {
  public static function match($stack, $details) {
    return strpos($details, $stack) !== false;
  }
}

abstract class Handler {
  protected $successor;

  public function forwardToSuccessor($job) {
    if ($this->successor) {
      $this->successor->handle($job);
    }
  }

  abstract public function handle($job);
}

class PHPStack extends Handler {
  public function __construct($successor) {
    $this->successor = $successor;
  }

  public function handle($job) {
    if (StackDetector::match('PHP', $job->requirements())) {
      // Notify PHP developers
      echo 'PHP Stack';
    } else {
      $this->forwardToSuccessor($job);
    }
  }
}

class JavaScriptStack extends Handler {
  public function __construct($successor) {
    $this->successor = $successor;
  }

  public function handle($job) {
    if (StackDetector::match('JavaScript', $job->requirements())) {
      // Notify JavaScript developers
      echo 'JavaScript Stack';
    } else {
      $this->forwardToSuccessor($job);
    }
  }
}

class JavaStack extends Handler {
  public function __construct($successor) {
    $this->successor = $successor;
  }

  public function handle($job) {
    if (StackDetector::match('Java', $job->requirements())) {
      // Notify Java developers
      echo 'Java Stack';
    } else {
      $this->forwardToSuccessor($job);
    }
  }
}

class DoNothing extends Handler {
  public function handle($job) {
    // Do nothing
    echo 'The request object is unhandled';
  }
}

// Chain of Job handler objects
$doNothing = new DoNothing();
$javaStack = new JavaStack($doNothing);
$javaScriptStack = new JavaScriptStack($javaStack);
$phpStack = new PHPStack($javaScriptStack);

// The request object to be handled
$job = new Job('PHP'); // Try changing the value to Python, JavaScript or Java

// Starts handling the Job object
$phpStack->handle($job);