Events

Events are the triggers that cause your state machine to transition from one state to another. They represent "something happened" in your system.

Sending Events

The basic way to send an event:

$machine->send(['type' => 'PAY']);

With payload data:

$machine->send([
    'type' => 'PAY',
    'amount' => 99.99,
    'method' => 'credit_card',
]);

Event Structure

Every event has a type that matches transitions:

// This event...
$machine->send(['type' => 'PAY']);

// ...matches this transition
'pending' => [
    'on' => [
        'PAY' => 'paid',  // type matches
    ],
]

Everything else in the event array is payload - data that actions and guards can access.

Accessing Event Data

Actions receive the event:

class ProcessPaymentAction extends ActionBehavior
{
    public function __invoke(
        ContextManager $context,
        EventBehavior $event
    ): void {
        $amount = $event->payload['amount'];
        $method = $event->payload['method'];
        // Process...
    }
}

Invalid Events

If you send an event with no matching transition, EventMachine throws NoTransitionDefinitionFoundException:

use Tarfinlabs\EventMachine\Exceptions\NoTransitionDefinitionFoundException;

try {
    $machine->send(['type' => 'PAY']);  // No transition for PAY
} catch (NoTransitionDefinitionFoundException $e) {
    // Handle invalid event
}

Internal Events

EventMachine fires internal events for lifecycle tracking:

Event	When
machine.start	Machine initialized
machine.finish	Machine reached final state

Learn More

For complete events documentation including:

• Custom event classes with validation
• Event versioning
• Raised events from actions
• Transactional events
• Actor tracking
• Complete internal events reference (18 events)
• Event source types (INTERNAL vs EXTERNAL)

See Handling Events.