WDT following AJAX requests

profiler.rst

@@ -21,3 +21,4 @@ install the profiler before using it:
     profiler/profiling_data
     profiler/matchers
     profiler/storage
+    profiler/wdt_follow_ajax

profiler/wdt_follow_ajax.rst

@@ -0,0 +1,40 @@
+.. index::
+    single: Profiling: WDT Auto-update after AJAX Request
+
+How to make the Web Debug Toolbar Auto-upate after AJAX Requests
+================================================================
+
+For single page applications it is often inconvenient to find the profiler
+information for the most recent request. It would be much more convient if it
+the toolbar would show the information from the most recent AJAX request
+instead of your initial page load.
+
+By setting the `Symfony-Debug-Toolbar-Replace` to a value of `1` in the
+AJAX request, the toolbar will be automatically reloaded for the request. The
+header can be set on the response object::
+
+    $response->headers->set('Symfony-Debug-Toolbar-Replace', 1);
+
+Only setting the header durring development
+-------------------------------------------
+
+Ideally this header should only be set durring development and not for
+production. This can be accomplished by setting the header in a
+:ref:`kernel.response <component-http-kernel-kernel-response>` event listener::
+
+    public function onKernelResponse(FilterResponseEvent $event)
+    {
+        $response = $event->getResponse();
+
+        $response->headers->set('Symfony-Debug-Toolbar-Replace', 1);
+    }
+
+.. seealso::
+
+    Read more Symfony events :ref:`/reference/events`.
+
+If you are using Symfony Flex, you should define your event listener service in the ``config/services_dev.yml`` file so that it only exists in the ``dev`` environment.
+
+.. seealso::
+
+    Read more on creating dev only services :ref:`/configuration/configuration_organization`.