• Symfony is a HTTP framework not an MVC framework
  • HTTP request -> Front Controller -> HttpKernel -> Routing Component -> Controller -> Model/View -> HttpFoundation response

Components Involved

  • HttpFoundation
    • Abstraciton of the request and the response
  • HttpKernel
    • Turns the request into a response

Routing Component

  • Maps a URL to a set of parameters
  • In D8 module_name.routing.yml


  • A callable responsible for communication with the model and view layers
  • In Symfony it must return a Response object
  • In D8 it can return an array

Event Dispatcher Component

  • Dispatch an Event
  • Listen/Subscribe to an event


Is an object which carries all the needed data into retrieve into each listener


  • Any valid PHP callable like a function name, an instance method, a static method or a closure
  • Event Listener != Event Subscriber
  • Event Subscriber
    • Have a defined list of events and functions to call on those events (defined by getSubcribedEvents())
    • Need to create a dispatcher and add the subscriber (addSubscriber())
  • Event Listener
    • Class that implements a function e.g. onKernelRequest(GetResponseEvent $event) (on is a standard prefix for event listener functions)
  • Events need to be dispatched

In Drupal

  • Create services to dispatch events

HttpKernel Events

  • kernel.request
  • kernel.controller
  • kernel.view
  • kernel.response
  • kernel.terminate
  • kernel.finish_request
  • kernel.exception

Service Container

  • Manages instantiation of service
  • Makes sure there is only one of each service


  • PHP object
  • Perform global task
  • Does not have any state
  • In D8
  • Can be tagged to have different behaviour (e.g. event_subscriber)


  • Global configuration