Andreas Hucks SensioLabs Deutschland CTO Symfony has a wide user base today. Most who work with Symfony on a daily basis have configured their own services, are fluent in configuring routing and validators. But what is actually going on under the hood? What happens when the configuration is parsed? What is a cache warmup? What happens to a request before hitting your controller? How does the HttpKernel work? Andreas will help us gain insight into the inner workings of the Symfony framework. If you have used Symfony, but have never built a compiler pass, a cache warmer, or are wondering how exactly the container is built, this talk is for you.

1. Symfony Under The Hood

2. Symfony Under The Hood
Andreas Hucks
CTO @ SensioLabs Germany

3. Version 4.0
November 2017

4. Directories 😍

5. Directories
├── bin
├── config
├── public
├── src
├── var
└── vendor

6. Directories
src
├── Controller
└── Kernel.php

7. No bundles 😱

8. Bundles are portable.
Your application is not.

9. Bundles
src
├── AdminBundle
├── ApiBundle
├── CartBundle
└── FrontendBundle

10. Bundles
src
├── AdminBundle
├── ApiBundle
├── CartBundle
├── FrontendBundle
└── [n-th]Bundle

11. Flex 😍

12. No Editions, no installer

13. Adding Doctrine
composer require orm

15. github.com/symfony/recipes

16. Autowiring 😍

17. Default services.yml
services:
_defaults:
autowire: true
autoconfigure: true
public: false
App:
resource: '../src/*'
exclude: '../src/{Entity,Migrations,Tests,Kernel.php}'
AppController:
resource: '../src/Controller'
tags: ['controller.service_arguments']
# Your own definitions here

18. Controllers
class GameController extends AbstractController
{
/**
* @Route(path="/", name="app_game")
*/
public function index(Runner $runner)
{
$game = $runner->loadGame();

20. Symfony Under The Hood

21. What to expect

22. Motivation

23. The Request
$kernel = new Kernel($env, $debug);
$request = Request::createFromGlobals();
$response = $kernel->handle($request);
$response->send();

24. HttpKernel
$kernel->handle($request);

25. Request-Response Flow
Request Response
Front
Controller Kernel

26. Symfony is not an
MVC framework

28. Symfony is a
Request-Response Framework

29. Request-Response Flow
Request Response
Front
Controller Kernel

30. Request-Response Flow
Kernel

31. Request-Response Flow
Kernel
kernel.request
kernel.controller
kernel.response
kernel.exceptio kernel.view
kernel.terminat

32. EventDispatcher
$dispatcher = new EventDispatcher();
$dispatcher->addListener('kernel.request', $callable);

33. EventDispatcher
$dispatcher->dispatch(
'kernel.request',
$responseEvent
);

34. EventDispatcher
$dispatcher->dispatch(
'kernel.request',
$responseEvent
);
payload
What happened.

35. Request-Response Flow
Kernel
kernel.request
kernel.controller
kernel.response
kernel.exceptio kernel.view
kernel.terminat

36. GetResponseEvent
class GetResponseEvent extends KernelEvent
{
public function getResponse()
{
return $this->response;
}
public function setResponse(Response $response)
{
$this->response = $response;
$this->stopPropagation();
}
kernel.request

37. RouterListener
/**
* @Route(path="/books/{id}", name="book_show")
*/
$params = [
'_controller' => ‘AppControllerBookController::showAction’,
'_route' => 'book_show',
'_route_params' => [
'id' => '37'
],
'id' => ’37'
];
kernel.request

38. RouterListener
$parameters = $this
->matcher->match($request->getPathInfo());
$request->attributes->add($parameters);
unset(
$parameters[‘_route'],
$parameters[‘_controller']
);
$request->attributes->set(
'_route_params',
$parameters
);
kernel.request

39. LocaleListener
$request = $event->getRequest();
$request->setDefaultLocale($this->defaultLocale);
if ($locale = $request->attributes->get('_locale')) {
$request->setLocale($locale);
}
kernel.request

40. Customize!
• Content Negotiation - Parse headers and add attribute
• Verify signed Cookies
• Redirects based on arbitrary criteria
• Custom Locale stuff
• … ?

41. Request-Response Flow
Kernel
kernel.request
kernel.controller
kernel.response
kernel.exceptio kernel.view
kernel.terminat

42. FilterControllerEvent
class FilterControllerEvent extends KernelEvent
{
public function getController()
{
return $this->controller;
}
public function setController(callable $controller)
{
$this->controller = $controller;
}
kernel.controller

43. ControllerListener
class ControllerListener implements EventSubscriberInterface
{
public function __construct(Reader $reader)
{
$this->reader = $reader;
}
public function onKernelController(FilterControllerEvent $event)
{
$controller = $event->getController();
// read annotations for class and method
$request = $event->getRequest();
foreach ($configurations as $key => $attributes) {
$request->attributes->set($key, $attributes);
}
kernel.controller

44. ParamConverterListener
class ParamConverterListener implements EventSubscriberInterface
{
/**
* @var ParamConverterManager
*/
private $manager;
kernel.controller

45. Request-Response Flow
Kernel
kernel.request
kernel.controller
kernel.response
kernel.exceptio kernel.view
kernel.terminat

46. Wait… Controllers?

47. HttpKernel
$response = call_user_func_array(
$controller,
$arguments
);

48. Request-Response Flow
Kernel
kernel.request
kernel.controller
kernel.response
kernel.exceptio kernel.view
kernel.terminat

49. GetResponseForControllerResultEvent
class GetResponseForControllerResultEvent extends GetResponseEvent
{
public function getControllerResult()
{
return $this->controllerResult;
}
public function setControllerResult($controllerResult)
{
$this->controllerResult = $controllerResult;
}
kernel.view

50. TemplateListener
public function onKernelView(
GetResponseForControllerResultEvent $event
) {
/* @var Template $template */
$request = $event->getRequest();
$template = $request->attributes->get(‘_template');
// …
$event->setResponse(
new Response(
$this->twig->render($template->getTemplate()),
$parameters
)
);
kernel.view

51. Customize!
• Auto serializing and encoding for web service responses
• Together with kernel.controller:
Action Domain Responder, other patterns?

52. Request-Response Flow
Kernel
kernel.request
kernel.controller
kernel.response
kernel.exceptio kernel.view
kernel.terminat

53. GetResponseForExceptionEvent
class GetResponseForExceptionEvent extends GetResponseEvent
{
public function getException()
{
return $this->exception;
}
kernel.exceptio

54. ExceptionListener
public function onKernelException(
GetResponseForExceptionEvent $event
) {
$exception = $event->getException();
$request = $event->getRequest();
$this->logException($exception
kernel.exceptio

55. Customize!
• Customize for every exception type you like
• Redirect for some errors
• “were you looking for…” suggestions on 404 pages
• Custom alerts
• … ?

56. Request-Response Flow
Kernel
kernel.request
kernel.controller
kernel.response
kernel.exceptio kernel.view
kernel.terminat

57. FilterResponseEvent
class FilterResponseEvent extends KernelEvent
{
public function getResponse()
{
return $this->response;
}
public function setResponse(Response $response)
{
$this->response = $response;
}
kernel.response

58. WebDebugToolbarListener
$response->headers->set(
'X-Debug-Token-Link',
$this->urlGenerator->generate(
‘_profiler',
array(
'token' => $response->headers->get(‘X-Debug-Token')
),
UrlGeneratorInterface::ABSOLUTE_URL
)
);
$this->injectToolbar($response, $request, $nonces);
kernel.response

59. SaveSessionListener
$session = $event->getRequest()->getSession();
if ($session && $session->isStarted()) {
$session->save();
$event->getResponse()
->setPrivate()
->setMaxAge(0)
->headers->addCacheControlDirective('must-revalidate');
}
kernel.response

60. Customize!
• Sign cookies
• Add custom headers
• … ?

61. Request-Response Flow
Kernel
kernel.request
kernel.controller
kernel.response
kernel.exceptio kernel.view
kernel.terminat

62. PostResponseEvent
class PostResponseEvent extends KernelEvent
{
public function getResponse()
{
return $this->response;
}
kernel.terminat

63. EmailSenderListener
public function onTerminate()
{
// send spooled Emails
kernel.terminat

64. Other Listeners kernel.request
• FirewallListener
• Collector Listeners

65. Recap
Request Response
Front
Controller Kernel

67. Thank you :)