Added use of addPrefix to define prefixes

Author: wouterj

components/routing/introduction.rst

@@ -142,23 +142,29 @@ Using Prefixes
 You can add routes or other instances of
 :class:`Symfony\\Component\\Routing\\RouteCollection` to *another* collection.
 This way you can build a tree of routes. Additionally you can define a prefix,
-default requirements, default options and hostname to all routes of a subtree::
+default requirements, default options and hostname to all routes of a subtree
+with the :method:`Symfony\\Component\\Routing\\RouteCollection::addPrefix`
+method::
 
  $rootCollection = new RouteCollection();
 
  $subCollection = new RouteCollection();
  $subCollection->add(...);
  $subCollection->add(...);
-
- $rootCollection->addCollection(
- $subCollection,
+ $subCollection->addPrefix(
  '/prefix', // prefix
  array(), // requirements
  array(), // options
  'admin.example.com', // hostname
  array('https') // schemes
  );
 
+ $rootCollection->addCollection($subCollection);
+
+.. versionadded:: 2.2
+ The ``addPrefixs`` method is added in Symfony2.2. This was part of the
+ ``addCollection`` method in older versions.
+
 Set the Request Parameters
 ~~~~~~~~~~~~~~~~~~~~~~~~~~