Show how to change the Session Attribute Bag type

Author: pbowyer

components/http_foundation/sessions.rst

@@ -207,6 +207,8 @@ Example::
     // ...
     $session->clear();
 
+.. _namespaced-attributes:
+
 Namespaced Attributes
 .....................
 

session.rst

@@ -201,5 +201,6 @@ More about Sessions
     session/locale_sticky_session
     session/php_bridge
     session/proxy_examples
+    session/attribute_bag
 
 .. _`HttpFoundation component`: https://symfony.com/components/HttpFoundation

session/attribute_bag.rst

@@ -0,0 +1,33 @@
+.. index::
+   single: Sessions, Attribute Bag
+
+Changing the Session Attribute Bag Provider
+===========================================
+
+Symfony uses attribute bags to represent values stored in the session. It ships 
+with the default :class:`Symfony\\Component\\HttpFoundation\\Session\\Attribute\\AttributeBag`, 
+which stores key-value pairs, and the 
+:class:`Symfony\\Component\\HttpFoundation\\Session\\Attribute\\NamespacedAttributeBag`, 
+which allows you to :ref:`set and fetch values using character-separated paths <namespaced-attributes>`.
+
+This is fully documented :doc:`in the component documentation </components/http_foundation/sessions>`.
+
+Changing the Attribute Bag in Symfony
+-------------------------------------
+
+To use a different attribute bag for your sessions, override the service 
+definition. In this example, we switch the default ``AttributeBag`` to the 
+``NamespacedAttributeBag``:
+
+.. configuration-block::
+
+    .. code-block:: yaml
+
+        # config/services.yaml
+        session:
+            class: Symfony\Component\HttpFoundation\Session\Session
+            arguments: ["@session.storage", "@session.namespacedattributebag", "@session.flash_bag"]
+
+        session.namespacedattributebag:
+            class: Symfony\Component\HttpFoundation\Session\Attribute\NamespacedAttributeBag
+