Symfony Kernel events vs Custom events - php

Question

In my controller after response I have to do some work. What is better to use:
1. Listen to kernel.terminate event
or
2. Dispatch my custom event
?
Why kernel.terminate?
As you can see, by calling $kernel->terminate after sending the
response, you will trigger the kernel.terminate event where you can
perform certain actions that you may have delayed in order to return
the response as quickly as possible to the client (e.g. sending
emails).
But on the other hand is it ok to check every request in my subscriber?

Answer 1

kernel.terminate happens after the response is sent, and can be useful for some "heavy" operations you can perform after the client has received the response. There are a few downsides however, mainly that if something goes wrong, there is no way to give the appropriate feedback to the user (for example to try again or to report a problem). Additionally, not all errors may be logged (see https://github.com/symfony/symfony/issues/19078).
Since you want to publish jobs to a Gearman queue, I would suggest avoiding using kernel.terminate, since typically publishing a job does not involve significant resources, and should be possible to do before sending the response. So you could trigger your custom event, or perhaps even avoid the event dispatcher completely by doing a more explicit call in your controller.

Answer 2

You won't be able to have your own event doing work after the response without using kernel.terminate. Because this is the only action that may occur after the response. We can confirm this by having a look at the front controller app.php:
$request = Request::createFromGlobals();
$response = $kernel->handle($request);
$response->send();
$kernel->terminate($request, $response);
As a note, kernel.terminate will work only if you use PHP-FPM. Otherwise, no solution outside of using some message queue.
Finally, a common pattern is to dynamically add a listener on kernel.terminate. From inside your controller, assuming you need to call my_service:
$myService = $this->get('my_service');
$this->get('event_dispatcher')->addListener('kernel.terminate', function (Event $event) use (myService) {
$myService->doSomething();
});