Events

The Event System

The event system is controlled by the EventManager. It is the central point of Doctrine's event listener system. Listeners are registered on the manager and events are dispatched through the manager.

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$evm = new EventManager();
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Now we can add some event listeners to the $evm. Let's create a TestEvent class to play around with.

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class TestEvent
{
    const preFoo = 'preFoo';
    const postFoo = 'postFoo';

    private $_evm;

    public $preFooInvoked = false;
    public $postFooInvoked = false;

    public function __construct($evm)
    {
        $evm->addEventListener(array(self::preFoo, self::postFoo), $this);
    }

    public function preFoo(EventArgs $e)
    {
        $this->preFooInvoked = true;
    }

    public function postFoo(EventArgs $e)
    {
        $this->postFooInvoked = true;
    }
}

// Create a new instance
$test = new TestEvent($evm);
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Events can be dispatched by using the dispatchEvent() method.

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$evm->dispatchEvent(TestEvent::preFoo);
$evm->dispatchEvent(TestEvent::postFoo);
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You can easily remove a listener with the removeEventListener() method.

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$evm->removeEventListener(array(self::preFoo, self::postFoo), $this);
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The Doctrine 2 event system also has a simple concept of event subscribers. We can define a simple TestEventSubscriber class which implements the \Doctrine\Common\EventSubscriber interface and implements a getSubscribedEvents() method which returns an array of events it should be subscribed to.

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class TestEventSubscriber implements \Doctrine\Common\EventSubscriber
{
    public $preFooInvoked = false;

    public function preFoo()
    {
        $this->preFooInvoked = true;
    }

    public function getSubscribedEvents()
    {
        return array(TestEvent::preFoo);
    }
}

$eventSubscriber = new TestEventSubscriber();
$evm->addEventSubscriber($eventSubscriber);
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Now when you dispatch an event, any event subscribers will be notified for that event.

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$evm->dispatchEvent(TestEvent::preFoo);
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Now you can test the $eventSubscriber instance to see if the preFoo() method was invoked.

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if ($eventSubscriber->preFooInvoked) {
    echo 'pre foo invoked!';
}
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prePersist

There are two ways for the prePersist event to be triggered. One is obviously when you call EntityManager#persist(). The event is also called for all cascaded associations.

There is another way for prePersist to be called, inside the flush() method when changes to associations are computed and this association is marked as cascade persist. Any new entity found during this operation is also persisted and prePersist called on it. This is called persistence by reachability.

In both cases you get passed a LifecycleEventArgs instance which has access to the entity and the entity manager.

The following restrictions apply to prePersist:

• If you are using a PrePersist Identity Generator such as sequences the ID value will NOT be available within any PrePersist events.
• Doctrine will not recognize changes made to relations in a prePersist event. This includes modifications to collections such as additions, removals or replacement.

preRemove

The preRemove event is called on every entity when its passed to the EntityManager#remove() method. It is cascaded for all associations that are marked as cascade delete.

There are no restrictions to what methods can be called inside the preRemove event, except when the remove method itself was called during a flush operation.

preFlush

preFlush is called at EntityManager#flush() before anything else. EntityManager#flush() can be called safely inside its listeners.

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use Doctrine\ORM\Event\PreFlushEventArgs;

class PreFlushExampleListener
{
    public function preFlush(PreFlushEventArgs $args)
    {
        // ...
    }
}
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onFlush

OnFlush is a very powerful event. It is called inside EntityManager#flush() after the changes to all the managed entities and their associations have been computed. This means, the onFlush event has access to the sets of:

• Entities scheduled for insert
• Entities scheduled for update
• Entities scheduled for removal
• Collections scheduled for update
• Collections scheduled for removal

To make use of the onFlush event you have to be familiar with the internal UnitOfWork API, which grants you access to the previously mentioned sets. See this example:

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class FlushExampleListener
{
    public function onFlush(OnFlushEventArgs $eventArgs)
    {
        $em = $eventArgs->getEntityManager();
        $uow = $em->getUnitOfWork();

        foreach ($uow->getScheduledEntityInsertions() as $entity) {

        }

        foreach ($uow->getScheduledEntityUpdates() as $entity) {

        }

        foreach ($uow->getScheduledEntityDeletions() as $entity) {

        }

        foreach ($uow->getScheduledCollectionDeletions() as $col) {

        }

        foreach ($uow->getScheduledCollectionUpdates() as $col) {

        }
    }
}
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The following restrictions apply to the onFlush event:

• If you create and persist a new entity in onFlush, then calling EntityManager#persist() is not enough. You have to execute an additional call to $unitOfWork->computeChangeSet($classMetadata, $entity).
• Changing primitive fields or associations requires you to explicitly trigger a re-computation of the changeset of the affected entity. This can be done by calling $unitOfWork->recomputeSingleEntityChangeSet($classMetadata, $entity).

postFlush

postFlush is called at the end of EntityManager#flush(). EntityManager#flush() can NOT be called safely inside its listeners.

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use Doctrine\ORM\Event\PostFlushEventArgs;

class PostFlushExampleListener
{
    public function postFlush(PostFlushEventArgs $args)
    {
        // ...
    }
}
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preUpdate

PreUpdate is the most restrictive to use event, since it is called right before an update statement is called for an entity inside the EntityManager#flush() method.

Changes to associations of the updated entity are never allowed in this event, since Doctrine cannot guarantee to correctly handle referential integrity at this point of the flush operation. This event has a powerful feature however, it is executed with a PreUpdateEventArgs instance, which contains a reference to the computed change-set of this entity.

This means you have access to all the fields that have changed for this entity with their old and new value. The following methods are available on the PreUpdateEventArgs:

• getEntity() to get access to the actual entity.
• getEntityChangeSet() to get a copy of the changeset array. Changes to this returned array do not affect updating.
• hasChangedField($fieldName) to check if the given field name of the current entity changed.
• getOldValue($fieldName) and getNewValue($fieldName) to access the values of a field.
• setNewValue($fieldName, $value) to change the value of a field to be updated.

A simple example for this event looks like:

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class NeverAliceOnlyBobListener
{
    public function preUpdate(PreUpdateEventArgs $eventArgs)
    {
        if ($eventArgs->getEntity() instanceof User) {
            if ($eventArgs->hasChangedField('name') && $eventArgs->getNewValue('name') == 'Alice') {
                $eventArgs->setNewValue('name', 'Bob');
            }
        }
    }
}
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You could also use this listener to implement validation of all the fields that have changed. This is more efficient than using a lifecycle callback when there are expensive validations to call:

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class ValidCreditCardListener
{
    public function preUpdate(PreUpdateEventArgs $eventArgs)
    {
        if ($eventArgs->getEntity() instanceof Account) {
            if ($eventArgs->hasChangedField('creditCard')) {
                $this->validateCreditCard($eventArgs->getNewValue('creditCard'));
            }
        }
    }

    private function validateCreditCard($no)
    {
        // throw an exception to interrupt flush event. Transaction will be rolled back.
    }
}
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Restrictions for this event:

• Changes to associations of the passed entities are not recognized by the flush operation anymore.
• Changes to fields of the passed entities are not recognized by the flush operation anymore, use the computed change-set passed to the event to modify primitive field values, e.g. use $eventArgs->setNewValue($field, $value); as in the Alice to Bob example above.
• Any calls to EntityManager#persist() or EntityManager#remove(), even in combination with the UnitOfWork API are strongly discouraged and don't work as expected outside the flush operation.

postUpdate, postRemove, postPersist

The three post events are called inside EntityManager#flush(). Changes in here are not relevant to the persistence in the database, but you can use these events to alter non-persistable items, like non-mapped fields, logging or even associated classes that are directly mapped by Doctrine.

postLoad

This event is called after an entity is constructed by the EntityManager.

Entity listeners class

An Entity Listener could be any class, by default it should be a class with a no-arg constructor.

• Different from Events an Entity Listener is invoked just to the specified entity
• An entity listener method receives two arguments, the entity instance and the lifecycle event.
• The callback method can be defined by naming convention or specifying a method mapping.
• When a listener mapping is not given the parser will use the naming convention to look for a matching method, e.g. it will look for a public preUpdate() method if you are listening to the preUpdate event.
• When a listener mapping is given the parser will not look for any methods using the naming convention.

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class UserListener
{
    public function preUpdate(User $user, PreUpdateEventArgs $event)
    {
        // Do something on pre update.
    }
}
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To define a specific event listener method (one that does not follow the naming convention) you need to map the listener method using the event type mapping:

Entity listeners resolver

Doctrine invokes the listener resolver to get the listener instance.

• A resolver allows you register a specific entity listener instance.
• You can also implement your own resolver by extending Doctrine\ORM\Mapping\DefaultEntityListenerResolver or implementing Doctrine\ORM\Mapping\EntityListenerResolver

Specifying an entity listener instance :

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// User.php

/** @Entity @EntityListeners({"UserListener"}) */
class User
{
    // ....
}

// UserListener.php
class UserListener
{
    public function __construct(MyService $service)
    {
        $this->service = $service;
    }

    public function preUpdate(User $user, PreUpdateEventArgs $event)
    {
        $this->service->doSomething($user);
    }
}

// register a entity listener.
$listener = $container->get('user_listener');
$em->getConfiguration()->getEntityListenerResolver()->register($listener);
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Implementing your own resolver :

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class MyEntityListenerResolver extends \Doctrine\ORM\Mapping\DefaultEntityListenerResolver
{
    public function __construct($container)
    {
        $this->container = $container;
    }

    public function resolve($className)
    {
        // resolve the service id by the given class name;
        $id = 'user_listener';

        return $this->container->get($id);
    }
}

// Configure the listener resolver only before instantiating the EntityManager
$configurations->setEntityListenerResolver(new MyEntityListenerResolver);
EntityManager::create(.., $configurations, ..);
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