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Error Handling

By default, the state machine returns false or null when a transition is not possible. However, you can configure it to throw exceptions instead.

Enabling Exception Throwing​

Use the throwErrorIfCannotTransition() method to enable exception throwing:

$stateMachine = FiniteStateMachine::createMachine()
    ->addTransition($transitionA_B)
    ->addTransition($transitionA_C)
    ->throwErrorIfCannotTransition();

Exception Behavior​

With canTransition()​

When exceptions are enabled, canTransition() will throw a TransitionException if the transition is not possible:

try {
    $stateMachine->canTransition($stA, $stD);
} catch (TransitionException $e) {
    echo $e->getMessage(); // "Cannot transition from A to D"
}

With autoTransitionFrom()​

When exceptions are enabled, autoTransitionFrom() will throw a TransitionException if no valid transition is found:

try {
    $stateMachine->autoTransitionFrom($stInitial, ["invalid" => "data"]);
} catch (TransitionException $e) {
    echo $e->getMessage(); // "There is not possible transitions from __VOID__ with the data provided"
}

Exception Class​

The TransitionException class extends the standard PHP Exception class:

use ByJG\StateMachine\TransitionException;