workflow with callbacks

gistfile1.php

<?php
namespace PHPWorkflow;

trait EventEmitterTrait {
    protected $listeners = [];
    public function on($event, callable $listener)
    {
        if (!isset($this->listeners[$event])) {
            $this->listeners[$event] = [];
        }
        $this->listeners[$event][] = $listener;
    }
    public function once($event, callable $listener)
    {
        $onceListener = function () use (&$onceListener, $event, $listener) {
            $this->removeListener($event, $onceListener);
            call_user_func_array($listener, func_get_args());
        };
        $this->on($event, $onceListener);
    }
    public function removeListener($event, callable $listener)
    {
        if (isset($this->listeners[$event])) {
            $index = array_search($listener, $this->listeners[$event], true);
            if (false !== $index) {
                unset($this->listeners[$event][$index]);
            }
        }
    }
    public function removeAllListeners($event = null)
    {
        if ($event !== null) {
            unset($this->listeners[$event]);
        } else {
            $this->listeners = [];
        }
    }
    public function listeners($event)
    {
        return isset($this->listeners[$event]) ? $this->listeners[$event] : [];
    }
    public function emit($event, array $arguments = [])
    {
        foreach ($this->listeners($event) as $listener) {
            call_user_func_array($listener, $arguments);
        }
    }
};

trait DefaultWorkflow {


	public $currentState = 0;
	protected $listTransitions;

	public function addTransitionFrom($state, $cb) {
		$this->listTransitions[$state] = $cb;
	}

	public function process($input) {
		$newstate = $this->listTransitions[$this->currentState]($input);
		if ($newstate == NULL) {
			return $this;
		}
		if ($newstate !== $this->currentState) {
			$this->emit('statechange', array($this->currentState, $newstate));
			$this->emit($newstate);
		}
		$this->currentState = $newstate;
		return $this;
	}
}

class DocumentPublish {

	use DefaultWorkflow;
	use EventEmitterTrait;

	public $currentState = '';

	public function __construct() {
		$this->addTransitionFrom('', function($input) {
			if ($input == 'promote') {
				return 'draft';
			}
		});

		$this->addTransitionFrom('draft', function($input) {
			if ($input == 'promote') {
				return 'review';
			}
		});

		$this->addTransitionFrom('review', function($input) {
			if ($input == 'promote') {
				return 'published';
			}
			if ($input == 'demote') {
				return 'draft';
			}
		});

		$this->addTransitionFrom('published', function($input) {
			if ($input == 'demote') {
				return 'review';
			}
		});
	}
}


$wf = new DocumentPublish();

$record = (object)array();// simulate active record pattern
$record->status = '';

$wf->on('draft', function() use($record) {
	$record->status = 'draft';
	//$record->save();
});

$wf->on('review', function() use($record) {
	$record->status = 'review';
	//$record->save();
});

$wf->on('published', function() use($record) {
	$record->status = 'published';
	//$record->save();
});

$wf->on('statechange', function($oldstate, $newstate) use($record) {
	echo "My state changed, it was $oldstate, it's now $newstate.\n";
});

echo 'workflow state: ['.$wf->currentState."]\n";
echo 'record status: ['.$record->status."]\n";

$wf->process('promote');
echo 'workflow state: ['.$wf->currentState."]\n";
echo 'record status: ['.$record->status."]\n";

$wf->process('promote');
echo 'workflow state: ['.$wf->currentState."]\n";
echo 'record status: ['.$record->status."]\n";

$wf->process('promote');
echo 'workflow state: ['.$wf->currentState."]\n";
echo 'record status: ['.$record->status."]\n";

$wf->process('demote');
echo 'workflow state: ['.$wf->currentState."]\n";
echo 'record status: ['.$record->status."]\n";

//output
/*
workflow state: []
record status: []
My state changed, it was , it's now draft.
workflow state: [draft]
record status: [draft]
My state changed, it was draft, it's now review.
workflow state: [review]
record status: [review]
My state changed, it was review, it's now published.
workflow state: [published]
record status: [published]
My state changed, it was published, it's now review.
workflow state: [review]
record status: [review]
*/