### Setup Doctrine Event Manager

Source: https://github.com/doctrine/event-manager/blob/2.0.x/docs/en/reference/index.rst

Demonstrates how to create an instance of the Doctrine Event Manager. This is the starting point for using the event system.

```php
use Doctrine\Common\EventManager;

$eventManager = new EventManager();
```

--------------------------------

### Install Doctrine Event Manager

Source: https://github.com/doctrine/event-manager/blob/2.0.x/docs/en/reference/index.rst

Installs the Doctrine Event Manager library using Composer. This is the primary method for adding the library to your project.

```sh
$ composer require doctrine/event-manager
```

--------------------------------

### Event Subscriber Example

Source: https://github.com/doctrine/event-manager/blob/2.0.x/docs/en/reference/index.rst

Illustrates the use of an Event Subscriber. The `TestEventSubscriber` class implements `Doctrine\Common\EventSubscriber` and defines which events it subscribes to via `getSubscribedEvents()`.

```php
use Doctrine\Common\EventSubscriber;

final class TestEventSubscriber implements EventSubscriber
{
    /** @var bool */
    public $preFooInvoked = false;

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

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

$eventSubscriber = new TestEventSubscriber();
$eventManager->addEventSubscriber($eventSubscriber);
```

--------------------------------

### Custom Event Listener Example

Source: https://github.com/doctrine/event-manager/blob/2.0.x/docs/en/reference/index.rst

Defines a custom event listener class 'TestEvent' that subscribes to 'preFoo' and 'postFoo' events. It includes methods to handle these events and flags to track invocation.

```php
use Doctrine\Common\EventArgs;
use Doctrine\Common\EventManager;

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

    /** @var EventManager */
    private $eventManager;

    /** @var bool */
    public $preFooInvoked = false;

    /** @var bool */
    public $postFooInvoked = false;

    public function __construct(EventManager $eventManager)
    {
        $eventManager->addEventListener([self::preFoo, self::postFoo], $this);
    }

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

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

// Create a new instance
$testEvent = new TestEvent($eventManager);
```

--------------------------------

### EventManager::getAllListeners() - Access All Listeners

Source: https://github.com/doctrine/event-manager/blob/2.0.x/UPGRADE.md

The `getAllListeners()` method is introduced to retrieve listeners for all events. This method should be used when you need to access the listeners of multiple events, replacing the previous behavior of calling `EventManager::getListeners()` without an event name.

```php
/**
 * Returns all listeners for all events.
 *
 * @return array
 */
public function getAllListeners(): array;
```

--------------------------------

### EventManager::getListeners() - Mandatory Event Parameter (v2.0)

Source: https://github.com/doctrine/event-manager/blob/2.0.x/UPGRADE.md

In version 2.0 of Doctrine Event Manager, the `$event` parameter for the `EventManager::getListeners()` method is now mandatory. This means you must specify the event name when retrieving listeners. For accessing listeners of all events, use the `getAllListeners()` method instead.

```php
/**
 * Returns the listeners for a given event.
 *
 * @param string $event The event name
 * @return array
 */
public function getListeners(string $event): array;
```

--------------------------------

### Deprecated EventManager::getListeners() without Event Name (v1.2)

Source: https://github.com/doctrine/event-manager/blob/2.0.x/UPGRADE.md

Version 1.2 of Doctrine Event Manager deprecated the practice of calling `EventManager::getListeners()` without providing an event name. Previously, this returned all listeners keyed by event name. The `getAllListeners()` method is now the recommended alternative for this functionality.

```php
// Deprecated in v1.2
// Use getAllListeners() instead
// public function getListeners();
```

--------------------------------

### Dispatching Event to Subscriber

Source: https://github.com/doctrine/event-manager/blob/2.0.x/docs/en/reference/index.rst

Dispatches an event ('preFoo') and shows how to verify if the event subscriber's corresponding method was invoked by checking its internal state.

```php
$eventManager->dispatchEvent(TestEvent::preFoo);

if ($eventSubscriber->preFooInvoked) {
    // the preFoo method was invoked
}
```

--------------------------------

### Dispatching Events

Source: https://github.com/doctrine/event-manager/blob/2.0.x/docs/en/reference/index.rst

Shows how to dispatch events using the `dispatchEvent()` method of the EventManager. This triggers the registered listeners for the specified events.

```php
$eventManager->dispatchEvent(TestEvent::preFoo);
$eventManager->dispatchEvent(TestEvent::postFoo);
```

--------------------------------

### Removing Event Listeners

Source: https://github.com/doctrine/event-manager/blob/2.0.x/docs/en/reference/index.rst

Demonstrates how to remove a specific listener from the EventManager using the `removeEventListener()` method. This stops the listener from receiving further event notifications.

```php
$eventManager->removeEventListener([TestEvent::preFoo, TestEvent::postFoo], $testEvent);
```

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