10. Events

Doctrine 2 features a lightweight event system that is part of the Common package. Doctrine uses it to dispatch system events, mainly lifecycle events. You can also use it for your own custom events.

10.1. 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.

<?php
$evm = new EventManager();

Now we can add some event listeners to the $evm. Let’s create a TestEvent class to play around with.

<?php
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);

Events can be dispatched by using the dispatchEvent() method.

<?php
$evm->dispatchEvent(TestEvent::preFoo);
$evm->dispatchEvent(TestEvent::postFoo);

You can easily remove a listener with the removeEventListener() method.

<?php
$evm->removeEventListener(array(self::preFoo, self::postFoo), $this);

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.

<?php
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);

Note

The array to return in the getSubscribedEvents method is a simple array with the values being the event names. The subscriber must have a method that is named exactly like the event.

Now when you dispatch an event, any event subscribers will be notified for that event.

<?php
$evm->dispatchEvent(TestEvent::preFoo);

Now you can test the $eventSubscriber instance to see if the preFoo() method was invoked.

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

10.1.1. Naming convention

Events being used with the Doctrine 2 EventManager are best named with camelcase and the value of the corresponding constant should be the name of the constant itself, even with spelling. This has several reasons:

  • It is easy to read.
  • Simplicity.
  • Each method within an EventSubscriber is named after the corresponding constant’s value. If the constant’s name and value differ it contradicts the intention of using the constant and makes your code harder to maintain.

An example for a correct notation can be found in the example TestEvent above.

10.2. Lifecycle Events

The EntityManager and UnitOfWork trigger a bunch of events during the life-time of their registered entities.

  • preRemove - The preRemove event occurs for a given entity before the respective EntityManager remove operation for that entity is executed. It is not called for a DQL DELETE statement.
  • postRemove - The postRemove event occurs for an entity after the entity has been deleted. It will be invoked after the database delete operations. It is not called for a DQL DELETE statement.
  • prePersist - The prePersist event occurs for a given entity before the respective EntityManager persist operation for that entity is executed. It should be noted that this event is only triggered on initial persist of an entity (i.e. it does not trigger on future updates).
  • postPersist - The postPersist event occurs for an entity after the entity has been made persistent. It will be invoked after the database insert operations. Generated primary key values are available in the postPersist event.
  • preUpdate - The preUpdate event occurs before the database update operations to entity data. It is not called for a DQL UPDATE statement.
  • postUpdate - The postUpdate event occurs after the database update operations to entity data. It is not called for a DQL UPDATE statement.
  • postLoad - The postLoad event occurs for an entity after the entity has been loaded into the current EntityManager from the database or after the refresh operation has been applied to it.
  • loadClassMetadata - The loadClassMetadata event occurs after the mapping metadata for a class has been loaded from a mapping source (annotations/xml/yaml). This event is not a lifecycle callback.
  • preFlush - The preFlush event occurs at the very beginning of a flush operation. This event is not a lifecycle callback.
  • onFlush - The onFlush event occurs after the change-sets of all managed entities are computed. This event is not a lifecycle callback.
  • postFlush - The postFlush event occurs at the end of a flush operation. This event is not a lifecycle callback.
  • onClear - The onClear event occurs when the EntityManager#clear() operation is invoked, after all references to entities have been removed from the unit of work. This event is not a lifecycle callback.

Warning

Note that the postLoad event occurs for an entity before any associations have been initialized. Therefore it is not safe to access associations in a postLoad callback or event handler.

Warning

Note that the postRemove event or any events triggered after an entity removal can receive an uninitializable proxy in case you have configured an entity to cascade remove relations. In this case, you should load yourself the proxy in the associated pre event.

You can access the Event constants from the Events class in the ORM package.

<?php
use Doctrine\ORM\Events;
echo Events::preUpdate;

These can be hooked into by two different types of event listeners:

  • Lifecycle Callbacks are methods on the entity classes that are called when the event is triggered. As of v2.4 they receive some kind of EventArgs instance.
  • Lifecycle Event Listeners and Subscribers are classes with specific callback methods that receives some kind of EventArgs instance.

The EventArgs instance received by the listener gives access to the entity, EntityManager and other relevant data.

Note

All Lifecycle events that happen during the flush() of an EntityManager have very specific constraints on the allowed operations that can be executed. Please read the Implementing Event Listeners section very carefully to understand which operations are allowed in which lifecycle event.

10.3. Lifecycle Callbacks

Lifecycle Callbacks are defined on an entity class. They allow you to trigger callbacks whenever an instance of that entity class experiences a relevant lifecycle event. More than one callback can be defined for each lifecycle event. Lifecycle Callbacks are best used for simple operations specific to a particular entity class’s lifecycle.

<?php

/** @Entity @HasLifecycleCallbacks */
class User
{
    // ...

    /**
     * @Column(type="string", length=255)
     */
    public $value;

    /** @Column(name="created_at", type="string", length=255) */
    private $createdAt;

    /** @PrePersist */
    public function doStuffOnPrePersist()
    {
        $this->createdAt = date('Y-m-d H:i:s');
    }

    /** @PrePersist */
    public function doOtherStuffOnPrePersist()
    {
        $this->value = 'changed from prePersist callback!';
    }

    /** @PostPersist */
    public function doStuffOnPostPersist()
    {
        $this->value = 'changed from postPersist callback!';
    }

    /** @PostLoad */
    public function doStuffOnPostLoad()
    {
        $this->value = 'changed from postLoad callback!';
    }

    /** @PreUpdate */
    public function doStuffOnPreUpdate()
    {
        $this->value = 'changed from preUpdate callback!';
    }
}

Note that the methods set as lifecycle callbacks need to be public and, when using these annotations, you have to apply the @HasLifecycleCallbacks marker annotation on the entity class.

If you want to register lifecycle callbacks from YAML or XML you can do it with the following.

User:
  type: entity
  fields:
# ...
    name:
      type: string(50)
  lifecycleCallbacks:
    prePersist: [ doStuffOnPrePersist, doOtherStuffOnPrePersist ]
    postPersist: [ doStuffOnPostPersist ]

In YAML the key of the lifecycleCallbacks entry is the event that you are triggering on and the value is the method (or methods) to call. The allowed event types are the ones listed in the previous Lifecycle Events section.

XML would look something like this:

<?xml version="1.0" encoding="UTF-8"?>

<doctrine-mapping xmlns="http://doctrine-project.org/schemas/orm/doctrine-mapping"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://doctrine-project.org/schemas/orm/doctrine-mapping
                          /Users/robo/dev/php/Doctrine/doctrine-mapping.xsd">

    <entity name="User">

        <lifecycle-callbacks>
            <lifecycle-callback type="prePersist" method="doStuffOnPrePersist"/>
            <lifecycle-callback type="postPersist" method="doStuffOnPostPersist"/>
        </lifecycle-callbacks>

    </entity>

</doctrine-mapping>

In XML the type of the lifecycle-callback entry is the event that you are triggering on and the method is the method to call. The allowed event types are the ones listed in the previous Lifecycle Events section.

When using YAML or XML you need to remember to create public methods to match the callback names you defined. E.g. in these examples doStuffOnPrePersist(), doOtherStuffOnPrePersist() and doStuffOnPostPersist() methods need to be defined on your User model.

<?php
// ...

class User
{
    // ...

    public function doStuffOnPrePersist()
    {
        // ...
    }

    public function doOtherStuffOnPrePersist()
    {
        // ...
    }

    public function doStuffOnPostPersist()
    {
        // ...
    }
}

10.4. Lifecycle Callbacks Event Argument

New in version 2.4.

Since 2.4 the triggered event is given to the lifecycle-callback.

With the additional argument you have access to the EntityManager and UnitOfWork APIs inside these callback methods.

<?php
// ...

class User
{
    public function preUpdate(PreUpdateEventArgs $event)
    {
        if ($event->hasChangedField('username')) {
            // Do something when the username is changed.
        }
    }
}

10.5. Listening and subscribing to Lifecycle Events

Lifecycle event listeners are much more powerful than the simple lifecycle callbacks that are defined on the entity classes. They sit at a level above the entities and allow you to implement re-usable behaviors across different entity classes.

Note that they require much more detailed knowledge about the inner workings of the EntityManager and UnitOfWork. Please read the Implementing Event Listeners section carefully if you are trying to write your own listener.

For event subscribers, there are no surprises. They declare the lifecycle events in their getSubscribedEvents method and provide public methods that expect the relevant arguments.

A lifecycle event listener looks like the following:

<?php
use Doctrine\Common\Persistence\Event\LifecycleEventArgs;

class MyEventListener
{
    public function preUpdate(LifecycleEventArgs $args)
    {
        $entity = $args->getObject();
        $entityManager = $args->getObjectManager();

        // perhaps you only want to act on some "Product" entity
        if ($entity instanceof Product) {
            // do something with the Product
        }
    }
}

A lifecycle event subscriber may looks like this:

<?php
use Doctrine\ORM\Events;
use Doctrine\Common\EventSubscriber;
use Doctrine\Common\Persistence\Event\LifecycleEventArgs;

class MyEventSubscriber implements EventSubscriber
{
    public function getSubscribedEvents()
    {
        return array(
            Events::postUpdate,
        );
    }

    public function postUpdate(LifecycleEventArgs $args)
    {
        $entity = $args->getObject();
        $entityManager = $args->getObjectManager();

        // perhaps you only want to act on some "Product" entity
        if ($entity instanceof Product) {
            // do something with the Product
        }
    }

Note

Lifecycle events are triggered for all entities. It is the responsibility of the listeners and subscribers to check if the entity is of a type it wants to handle.

To register an event listener or subscriber, you have to hook it into the EventManager that is passed to the EntityManager factory:

<?php
$eventManager = new EventManager();
$eventManager->addEventListener(array(Events::preUpdate), new MyEventListener());
$eventManager->addEventSubscriber(new MyEventSubscriber());

$entityManager = EntityManager::create($dbOpts, $config, $eventManager);

You can also retrieve the event manager instance after the EntityManager was created:

<?php
$entityManager->getEventManager()->addEventListener(array(Events::preUpdate), new MyEventListener());
$entityManager->getEventManager()->addEventSubscriber(new MyEventSubscriber());

10.6. Implementing Event Listeners

This section explains what is and what is not allowed during specific lifecycle events of the UnitOfWork. Although you get passed the EntityManager in all of these events, you have to follow these restrictions very carefully since operations in the wrong event may produce lots of different errors, such as inconsistent data and lost updates/persists/removes.

For the described events that are also lifecycle callback events the restrictions apply as well, with the additional restriction that (prior to version 2.4) you do not have access to the EntityManager or UnitOfWork APIs inside these events.

10.6.1. 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.

10.6.2. 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.

10.6.3. preFlush

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

<?php

use Doctrine\ORM\Event\PreFlushEventArgs;

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

10.6.4. 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:

<?php
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) {

        }
    }
}

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).

10.6.5. postFlush

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

<?php

use Doctrine\ORM\Event\PostFlushEventArgs;

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

10.6.6. 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:

<?php
class NeverAliceOnlyBobListener
{
    public function preUpdate(PreUpdateEventArgs $eventArgs)
    {
        if ($eventArgs->getEntity() instanceof User) {
            if ($eventArgs->hasChangedField('name') && $eventArgs->getNewValue('name') == 'Alice') {
                $eventArgs->setNewValue('name', 'Bob');
            }
        }
    }
}

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:

<?php
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.
    }
}

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.

10.6.7. 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.

10.6.8. postLoad

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

10.7. Entity listeners

New in version 2.4.

An entity listener is a lifecycle listener class used for an entity.

  • The entity listener’s mapping may be applied to an entity class or mapped superclass.
  • An entity listener is defined by mapping the entity class with the corresponding mapping.
  • PHP
    <?php
    namespace MyProject\Entity;
    
    /** @Entity @EntityListeners({"UserListener"}) */
    class User
    {
        // ....
    }
    
  • XML
    <doctrine-mapping>
        <entity name="MyProject\Entity\User">
            <entity-listeners>
                <entity-listener class="UserListener"/>
            </entity-listeners>
            <!-- .... -->
        </entity>
    </doctrine-mapping>
    
  • YAML
    MyProject\Entity\User:
      type: entity
      entityListeners:
        UserListener:
      # ....
    

10.7.1. Entity listeners class

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

  • Different from Implementing Event Listeners 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.
<?php
class UserListener
{
    public function preUpdate(User $user, PreUpdateEventArgs $event)
    {
        // Do something on pre update.
    }
}

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:

  • PHP
    <?php
    class UserListener
    {
        /** @PrePersist */
        public function prePersistHandler(User $user, LifecycleEventArgs $event) { // ... }
    
        /** @PostPersist */
        public function postPersistHandler(User $user, LifecycleEventArgs $event) { // ... }
    
        /** @PreUpdate */
        public function preUpdateHandler(User $user, PreUpdateEventArgs $event) { // ... }
    
        /** @PostUpdate */
        public function postUpdateHandler(User $user, LifecycleEventArgs $event) { // ... }
    
        /** @PostRemove */
        public function postRemoveHandler(User $user, LifecycleEventArgs $event) { // ... }
    
        /** @PreRemove */
        public function preRemoveHandler(User $user, LifecycleEventArgs $event) { // ... }
    
        /** @PreFlush */
        public function preFlushHandler(User $user, PreFlushEventArgs $event) { // ... }
    
        /** @PostLoad */
        public function postLoadHandler(User $user, LifecycleEventArgs $event) { // ... }
    }
    
  • XML
    <doctrine-mapping>
        <entity name="MyProject\Entity\User">
             <entity-listeners>
                <entity-listener class="UserListener">
                    <lifecycle-callback type="preFlush"      method="preFlushHandler"/>
                    <lifecycle-callback type="postLoad"      method="postLoadHandler"/>
    
                    <lifecycle-callback type="postPersist"   method="postPersistHandler"/>
                    <lifecycle-callback type="prePersist"    method="prePersistHandler"/>
    
                    <lifecycle-callback type="postUpdate"    method="postUpdateHandler"/>
                    <lifecycle-callback type="preUpdate"     method="preUpdateHandler"/>
    
                    <lifecycle-callback type="postRemove"    method="postRemoveHandler"/>
                    <lifecycle-callback type="preRemove"     method="preRemoveHandler"/>
                </entity-listener>
            </entity-listeners>
            <!-- .... -->
        </entity>
    </doctrine-mapping>
    
  • YAML
    MyProject\Entity\User:
      type: entity
      entityListeners:
        UserListener:
          preFlush: [preFlushHandler]
          postLoad: [postLoadHandler]
    
          postPersist: [postPersistHandler]
          prePersist: [prePersistHandler]
    
          postUpdate: [postUpdateHandler]
          preUpdate: [preUpdateHandler]
    
          postRemove: [postRemoveHandler]
          preRemove: [preRemoveHandler]
      # ....
    

10.7.2. 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 :

<?php
// 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);

Implementing your own resolver :

<?php
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, ..);

10.8. Load ClassMetadata Event

When the mapping information for an entity is read, it is populated in to a ClassMetadataInfo instance. You can hook in to this process and manipulate the instance.

<?php
$test = new TestEvent();
$metadataFactory = $em->getMetadataFactory();
$evm = $em->getEventManager();
$evm->addEventListener(Events::loadClassMetadata, $test);

class TestEvent
{
    public function loadClassMetadata(\Doctrine\ORM\Event\LoadClassMetadataEventArgs $eventArgs)
    {
        $classMetadata = $eventArgs->getClassMetadata();
        $fieldMapping = array(
            'fieldName' => 'about',
            'type' => 'string',
            'length' => 255
        );
        $classMetadata->mapField($fieldMapping);
    }
}
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