A Simple PHP Finite State Machine
Finite is a Simple State Machine, written in PHP. It can manage any Stateful object by defining states and transitions between these states.
As of version 2, Finite is a low-deps and lightweight state machine library, thanks to the use of PHP Enums.
$ composer req yohang/finiteenum DocumentState: string implements State
{
case DRAFT = 'draft';
case PUBLISHED = 'published';
case REPORTED = 'reported';
case DISABLED = 'disabled';
public static function getTransitions(): array
{
return [
new Transition('publish', [self::DRAFT], self::PUBLISHED),
new Transition('clear', [self::REPORTED, self::DISABLED], self::PUBLISHED),
new Transition('report', [self::PUBLISHED], self::REPORTED),
new Transition('disable', [self::REPORTED, self::PUBLISHED], self::DISABLED),
];
}
}
Your stateful object just need to have a state property
class Document
{
private DocumentState $state = DocumentState::DRAFT;
public function getState(): DocumentState
{
return $this->state;
}
public function setState(DocumentState $state): void
{
$this->state = $state;
}
}use Finite\StateMachine;
$document = new Document;
$sm = new StateMachine;
// Can we process a transition ?
$sm->can($document, 'publish');
// Apply a transition
$sm->apply($document, 'publish');
Finite < 2.0 had properties on states. A metadata mechanism that allowed to add business properties on states to define the behavior of on object, depending on its state.
The idea behind this was to avoid to test the state in your domain code (A controller must not throw a 404 if the state is draft. But it can throw a 404 if the current state does not have a "visible" property. That was the idea).
Finite 2 does not needs this. PHP Enums can have methods. So, replace your properties with simple methods on your state.
enum DocumentState: string implements State
{
// ...
public function isDeletable(): bool
{
return in_array($this, [self::DRAFT, self::DISABLED]);
}
public function isPrintable(): bool
{
return in_array($this, [self::PUBLISHED, self::REPORTED]);
}
}After that, you can use theses methods on your object, even without instantiating the state machine.
var_dump($document->getState()->isDeletable());
var_dump($document->getState()->isPrintable());Finite dispatches PSR-14 events. You can listen to them to add custom logic or block transitions.
…Register the bundle in config/bundles.php:
return [
// ...
Finite\Extension\Symfony\Bundle\FiniteBundle::class => ['all' => true],
];This automatically registers the StateMachine service and the Twig extension.
{# Check if a transition is available #}
{% if finite_can(document, 'publish') %}
<a href="...">Publish</a>
{% endif %}
{# List all reachable transitions #}
<ul>
{% for transition in finite_reachable_transitions(document) %}
<li>{{ transition.name }}</li>
{% endfor %}
</ul>Dump your graph to visualize it:
php bin/console finite:state-machine:dump "App\State\DocumentState" mermaidThis library is licensed under the MIT License.
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