A Simple PHP Workflow Engine (State Machine)

This is a PHP engine that can take a subject (entity, document, db record) that has an enum property (either a native PHP enum or Konekt Enum) that represents the state of the subject.

The workflow is defined around the possible states (values of the enum).

Transitions can be defined from one state to another.

Example

class OrderWorkflow extends \Vanilo\Workflow\Draft
{
    private static string $enumClass = OrderStatus::class;
    private static string $property = 'status';

    private static array $graph = [
        'name' => 'Order Workflow',
        'transitions' => [
            'prepare' => [
                'from' => [OrderStatus::NEW, OrderStatus::PENDING],
                'to' => OrderStatus::PROCESSING,
            ],
            'ship' => [
                'from' => [OrderStatus::PROCESSING],
                'to' => OrderStatus::COMPLETED,
            ],
            'cancel' => [
                'from' => ['*'],
                'to' => OrderStatus::CANCELED,
            ],
        ],    
    ];
}

$order = Order::find(1);
echo $order->status->value;
// PROCESSING

$workflow = OrderWorkflow::for($order);
$workflow->can('prepare');
// false
$workflow->can('cancel');
// true

$workflow->allowedTransitions()
// ['ship, 'cancel']

$workflow->execute('ship');
echo $order->status->value;
// COMPLETED

Writing Explicit Transitions

By default, executing transitions will mutate the subject's state to the desired end state.

But it's also possible to explicitly define methods that will be called instead.

class OrderWorkflow extends \Vanilo\Workflow\Draft
{
    private static string $enumClass = OrderStatus::class;
    private static string $property = 'status';

    private static array $graph = [
        'transitions' => [
            'cancel' => [
                'from' => ['*'],
                'to' => OrderStatus::CANCELED,
            ],
        ],
    ];
    
    
    public function cancel(Order $order): void
    {
        foreach ($order->items as $item) {
            Inventory::release($item->sku, $item->quantity)
        }
    
        $order->status = OrderStatus::CANCELED;
        $orders->save();
        
        Event::dispatch(new OrderCanceled($order));  
    }
}