State pattern in PHP

AbstractState.php

<?php
abstract class AbstractState implements StateInterface
{
    /**
     * @var WorkflowInterface
     */
    private $workflow;

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

    public function methodA()
    {
        throw new \Exception('You should not call that method in that state');
    }

    public function methodB()
    {
        throw new \Exception('You should not call that method in that state');
    }
}

AbstractWorkflow.php

<?php
abstract class AbstractWorkflow
{
    /**
     * @var StateInterface
     */
    private $state;

    public function setState(StateInterface $state)
    {
        $this->state = $state;
    }
}

AState.php

<?php
class AState extends AbstractState implements StateInterface
{
    public function methodA()
    {
        try {
            // Do stuff
            // ...
        } catch (\Exception $e) {
            $this->workflow->setState(new ErrorState($this->workflow, $this));

            return $this->workflow;
        }

        $this->workflow->setState(new BState($this->workflow));

        return $this->workflow;
    }
}

BState.php

<?php
class BState extends AbstractState implements StateInterface
{
    public function methodB()
    {
        try {
            // Do stuff
            // ...
        } catch (\Exception $e) {
            $this->workflow->setState(new ErrorState($this->workflow, $this));

            return $this->workflow;
        }

        $this->workflow->setState(new EndState($this->workflow));

        return $this->workflow;
    }
}

EndState.php

<?php
class EndState extends AbstractState implements StateInterface
{
}

ErrorState.php

<?php
class ErrorState extends AbstractState implements StateInterface
{
    /**
     * @var StateInterface
     */
    private $previousState;

    public function __construct(WorkflowInterface $workflow, StateInterface $previousState = null)
    {
        parent::__construct($workflow);
        $this->previousState = $previousState;
    }
}

main.php

<?php
$workflow = new MyWorkflow();
$workflow->methodA(); // Switches from state A to state B
$workflow->methodB(); // Switches from state B to EndState

$workflow = new MyWorkflow();
$workflow->methodB(); // Switches from state A to Error state

$workflow = new MyWorkflow();
$workflow->methodA(); // Switches from state A to state B
$workflow->methodB(); // Switches from state B to Error state

MyWorkflow.php

<?php
class MyWorkflow extends AbstractWorkflow implements WorkflowInterface
{
    public function __construct()
    {
        $this->state = new AState($this);
    }

    public function methodA()
    {
        return $this->state->methodA();
    }

    public function methodB()
    {
        return $this->state->methodB();
    }
}

StateInterface.php

<?php
interface StateInterface
{
    public function methodA();
    public function methodB();
}

WorkflowInterface.php

<?php
interface WorkflowInterface
{
    public function setState(StateInterface $state);
}