Doctrine Events

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Doctrine, the set of PHP libraries used by Symfony to work with databases, provides a lightweight event system to update entities during the application execution. These events, called lifecycle events, allow to perform tasks such as "update the createdAt property automatically right before persisting entities of this type".

Doctrine triggers events before/after performing the most common entity operations (e.g. prePersist/postPersist, preUpdate/postUpdate) and also on other common tasks (e.g. loadClassMetadata, onClear).

There are different ways to listen to these Doctrine events:

  • Lifecycle callbacks, they are defined as public methods on the entity classes. They can't use services, so they are intended for very simple logic related to a single entity;
  • Entity listeners, they are defined as classes with callback methods for the events you want to respond to. They can use services, but they are only called for the entities of a certain class, so they are ideal for complex event logic related to a single entity;
  • Lifecycle listeners, they are similar to entity listeners but their event methods are called for all entities, not only those of a certain type. They are ideal to share event logic between entities.

The performance of each type of listener depends on how many entities applies to: lifecycle callbacks are faster than entity listeners, which in turn are faster than lifecycle listeners.

This article only explains the basics about Doctrine events when using them inside a Symfony application. Read the official docs about Doctrine events to learn everything about them.

See also

This article covers listeners and subscribers for Doctrine ORM. If you are using ODM for MongoDB, read the DoctrineMongoDBBundle documentation.

Doctrine Lifecycle Callbacks

Lifecycle callbacks are defined as public methods inside the entity you want to modify. For example, suppose you want to set a createdAt date column to the current date, but only when the entity is first persisted (i.e. inserted). To do so, define a callback for the prePersist Doctrine event:

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// src/Entity/Product.php
namespace App\Entity;

use Doctrine\ORM\Mapping as ORM;

// When using attributes, don't forget to add #[ORM\HasLifecycleCallbacks]
// to the class of the entity where you define the callback

#[ORM\Entity]
#[ORM\HasLifecycleCallbacks]
class Product
{
    // ...

    #[ORM\PrePersist]
    public function setCreatedAtValue(): void
    {
        $this->createdAt = new \DateTimeImmutable();
    }
}

Note

Some lifecycle callbacks receive an argument that provides access to useful information such as the current entity manager (e.g. the preUpdate callback receives a PreUpdateEventArgs $event argument).

Doctrine Entity Listeners

Entity listeners are defined as PHP classes that listen to a single Doctrine event on a single entity class. For example, suppose that you want to send some notifications whenever a User entity is modified in the database.

First, define a PHP class that handles the postUpdate Doctrine event:

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// src/EventListener/UserChangedNotifier.php
namespace App\EventListener;

use App\Entity\User;
use Doctrine\ORM\Event\PostUpdateEventArgs;

class UserChangedNotifier
{
    // the entity listener methods receive two arguments:
    // the entity instance and the lifecycle event
    public function postUpdate(User $user, PostUpdateEventArgs $event): void
    {
        // ... do something to notify the changes
    }
}

Then, add the #[AsEntityListener] attribute to the class to enable it as a Doctrine entity listener in your application:

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// src/EventListener/UserChangedNotifier.php
namespace App\EventListener;

// ...
use App\Entity\User;
use Doctrine\Bundle\DoctrineBundle\Attribute\AsEntityListener;
use Doctrine\ORM\Events;

#[AsEntityListener(event: Events::postUpdate, method: 'postUpdate', entity: User::class)]
class UserChangedNotifier
{
    // ...
}

Alternatively, if you prefer to not use PHP attributes, you must configure a service for the entity listener and tag it with the doctrine.orm.entity_listener tag as follows:

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# config/services.yaml
services:
    # ...

    App\EventListener\UserChangedNotifier:
        tags:
            -
                # these are the options required to define the entity listener
                name: 'doctrine.orm.entity_listener'
                event: 'postUpdate'
                entity: 'App\Entity\User'

                # these are other options that you may define if needed

                # set the 'lazy' option to TRUE to only instantiate listeners when they are used
                # lazy: true

                # set the 'entity_manager' option if the listener is not associated to the default manager
                # entity_manager: 'custom'

                # by default, Symfony looks for a method called after the event (e.g. postUpdate())
                # if it doesn't exist, it tries to execute the '__invoke()' method, but you can
                # configure a custom method name with the 'method' option
                # method: 'checkUserChanges'

Doctrine Lifecycle Listeners

Lifecycle listeners are defined as PHP classes that listen to a single Doctrine event on all the application entities. For example, suppose that you want to update some search index whenever a new entity is persisted in the database. To do so, define a listener for the postPersist Doctrine event:

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// src/EventListener/SearchIndexer.php
namespace App\EventListener;

use App\Entity\Product;
use Doctrine\ORM\Event\PostPersistEventArgs;

class SearchIndexer
{
    // the listener methods receive an argument which gives you access to
    // both the entity object of the event and the entity manager itself
    public function postPersist(PostPersistEventArgs $args): void
    {
        $entity = $args->getObject();

        // if this listener only applies to certain entity types,
        // add some code to check the entity type as early as possible
        if (!$entity instanceof Product) {
            return;
        }

        $entityManager = $args->getObjectManager();
        // ... do something with the Product entity
    }
}

Note

In previous Doctrine versions, instead of PostPersistEventArgs, you had to use LifecycleEventArgs, which was deprecated in Doctrine ORM 2.14.

Then, add the #[AsDoctrineListener] attribute to the class to enable it as a Doctrine listener in your application:

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// src/EventListener/SearchIndexer.php
namespace App\EventListener;

use Doctrine\Bundle\DoctrineBundle\Attribute\AsDoctrineListener;
use Doctrine\ORM\Events;

#[AsDoctrineListener(event: Events::postPersist, priority: 500, connection: 'default')]
class SearchIndexer
{
    // ...
}

Alternatively, if you prefer to not use PHP attributes, you must enable the listener in the Symfony application by creating a new service for it and tagging it with the doctrine.event_listener tag:

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// src/EventListener/SearchIndexer.php
namespace App\EventListener;

use Doctrine\Bundle\DoctrineBundle\Attribute\AsDoctrineListener;
use Doctrine\ORM\Event\PostPersistEventArgs;

#[AsDoctrineListener('postPersist'/*, 500, 'default'*/)]
class SearchIndexer
{
    public function postPersist(PostPersistEventArgs $event): void
    {
        // ...
    }
}

2.8.0

The AsDoctrineListener attribute was introduced in DoctrineBundle 2.8.0.

Tip

Symfony loads (and instantiates) Doctrine listeners only when the related Doctrine event is actually fired; whereas Doctrine subscribers are always loaded (and instantiated) by Symfony, making them less performant.

Tip

The value of the connection option can also be a configuration parameter.

Doctrine Lifecycle Subscribers

6.3

Lifecycle subscribers are deprecated starting from Symfony 6.3.

This was another way of listening to events provided by Doctrine. However, they were deprecated in Symfony 6.3 and it's no longer recommended to use them. Instead, use any of the other alternatives shown above.

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.
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