[HttpFoundation] Add doc for Request::getContent() method

Author: bicpi

components/http_foundation/introduction.rst

@@ -168,14 +168,22 @@ argument::
 
 .. _component-foundation-attributes:
 
-Finally, you can also store additional data in the request,
-thanks to the public ``attributes`` property, which is also an instance of
+Thanks to the public ``attributes`` property, you can store additional data
+in the request, which is also an instance of
 :class:`Symfony\\Component\\HttpFoundation\\ParameterBag`. This is mostly used
 to attach information that belongs to the Request and that needs to be
 accessed from many different points in your application. For information
 on how this is used in the Symfony2 framework, see
 :ref:`the Symfony2 book <book-fundamentals-attributes>`.
 
+Finally, the raw data sent with the request body can be accessed using
+:method:`Symfony\\Component\\HttpFoundation\\Request::getContent()`::
+
+    $content = $request->getContent();
+
+For instance, this may be useful to process a JSON string sent to the
+application by a remote service using the HTTP POST method.
+
 Identifying a Request
 ~~~~~~~~~~~~~~~~~~~~~