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eZ Publish (5.x)

eZ Publish 5.x | For eZ Platform & eZ Studio topics see Technical manual and User manual, for eZ Publish 4.x and Legacy topics see eZ Publish legacy

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titleVersion compatibility

This recipe is compatible with eZ Publish 5.2 / 2013.07

Table of Contents


When you interact with the Public API, and with the content Repository in particular, Signals may be sent out, allowing you to react on actions triggered by the Repository. Those signals can be received by dedicated services called Slots.


To learn more about SignalSlot in eZ Publish, please refer to the dedicated documentation page.

Signals reference

This recipe will describe how to register a Slot for a dedicated Signal.

Registering a Slot for a given Signal

As described in the SignalSlot documentation, a Slot is roughly like an event listener and must extend eZ\Publish\Core\SignalSlot\Slot.

A typical implementation is the following:

Code Block
namespace Acme\TestBundle\Slot;
use eZ\Publish\Core\SignalSlot\Slot as BaseSlot;
use eZ\Publish\API\Repository\Repository;
use eZ\Publish\SignalSlot\Signal;
class OnPublishSlot extends BaseSlot
     * @var \eZ\Publish\API\Repository\ContentService
    private $contentService;

    public function __construct( ContentService $contentService )
        $this->contentService = $contentService;
    public function receive( Signal $signal )
        if ( !$signal instanceof Signal\ContentService\PublishVersionSignal )

        // Load published content
        $content = $this->contentService->loadContent( $signal->contentId, null, $signal->versionNo );
        // Do stuff with it...

OnPublishSlot now needs to be registered as a service in the ServiceContainer and identified as a valid Slot:

Code Block
titleservices.yml (in your bundle)
    my.onpublish_slot.class: Acme\TestBundle\Slot\OnPublishSlot
        class: %my.onpublish_slot.class%
        arguments: [@ezpublish.api.service.content]
            - { name: ezpublish.api.slot, signal: ContentService\PublishVersionSignal }

Service tag ezpublish.api.slot identifies your service as a valid Slot. The signal part (mandatory) says that this slot is listening to ContentService\PublishVersionSignal (shortcut for \eZ\Publish\Core\SignalSlot\Signal\ContentService\PublishVersionSignal).


Internal signals emitted by Repository services are always relative to eZ\Publish\Core\SignalSlot\Signal namespace.

Hence ContentService\PublishVersionSignal means eZ\Publish\Core\SignalSlot\Signal\ContentService\PublishVersionSignal.


You can register a slot for any kind of signal by setting signal to * in the service tag.

Using a basic Symfony event listener

eZ Publish comes with a generic slot that converts signals (including ones defined by user code) to regular event objects and expose them via the EventDispatcher. This makes it possible to implement a simple event listener/subscriber if you're more comfortable with this approach.

All you need to do is to implement an event listener or subscriber and register it.

Simple example

This very simple example will just log the received signal.

Code Block
titleservices.yml (in your bundle)
    my.signal_listener.class: Acme\TestBundle\EventListener\SignalListener
        class: %my.signal_listener.class%
        arguments: [@logger]
            - { name: kernel.event_subscriber }
Code Block
namespace Acme\TestBundle\EventListener;

use eZ\Publish\Core\MVC\Symfony\Event\SignalEvent;
use eZ\Publish\Core\MVC\Symfony\MVCEvents;
use Psr\Log\LoggerInterface;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;

class SignalListener implements EventSubscriberInterface
     * @var \Psr\Log\LoggerInterface
    private $logger;

    public function __construct( LoggerInterface $logger )
        $this->logger = $logger;

    public function onAPISignal( SignalEvent $event )
        $signal = $event->getSignal();
        // You may want to check the signal type here to react accordingly
        $this->logger->debug( 'Received Signal: ' . print_r( $signal, true ) );

    public static function getSubscribedEvents()
        return array(
            MVCEvents::API_SIGNAL => 'onAPISignal'