use \Rezzza\Workflow\Graph;
use \Rezzza\Workflow\State;
use \Rezzza\Workflow\Workflow;
use \Rezzza\Workflow\Exception;

$graph = new Graph();
$graph
    ->addState('empty', new State\NextOne())                                     // can go to filled
    ->addState('filled', new State\StateCollection(array('empty', 'confirmed'))) // can go to empty or confirmed
    ->addState('confirmed', new State\NextOne())                                 // can go to pending transaction
    ->addState('pending_transaction', new State\NextAll())                       // can go to failing_transaction or success_transaction
    ->addState('failing_transaction', new State\End())
    ->addState('success_transaction', new State\End())

$cart     = new Acme\ECommerce\Path\To\Cart();
$workflow = new Workflow($graph, $cart, 'status');
$states   = $workflow->getAuthorizedStates();

try {
    $workflow->moveToState('filled');
} catch (Exception\ConflictException e) {
    // it seems you want to add a state already setted.
} catch (Exception\WorkflowException $e) {
    // you try to set a state not authorized.
}

use Rezzza\Workflow\Specification\SpecificationInterface;

class ConfirmableSpecification implements SpecificationInterface
{
    public function isSatisfiedBy($object)
    {
        return $object->hasUserAuthenticated();
    }
}

$graph = new Graph();
$graph
    //........
    ->addState('confirmed', new State\NextOne(new ConfirmableSpecification()))
    //.........