Some explanations on how it works now:
* The Session is an optional dependency of the Request. If you create the
Request yourself (which is mandatory now in the front controller) and if
you don't inject a Session yourself (which is recommended if you want the
session to be configured via dependency injection), the Symfony2 Kernel
will associate the Session configured in the Container with the Request
automatically.
* When duplicating a request, the session is shared between the parent and
the child (that's because duplicated requests are sub-requests of the main
one most of the time.) Notice that when you use ::create(), the behavior is
the same as for the constructor; no session is attached to the Request.
* Symfony2 tries hard to not create a session cookie when it is not needed
but a Session object is always available (the cookie is only created when
"something" is stored in the session.)
* Symfony2 only starts a session when:
* A session already exists in the request ($_COOKIE[session_name()] is
defined -- this is done by RequestListener);
* There is something written in the session object (the cookie will be sent
to the Client).
* Notice that reading from the session does not start the session anymore (as
we don't need to start a new session to get the default values, and because
if a session exists, it has already been started by RequestListener.)
Old notation: bundle:section:name.format:renderer (where both format and renderer are optional)
New notation: bundle:section:name.format.renderer (where only format is optional)
Valid new template names: Blog:Post:index.php, Blog:Post:index.xml.php
The new notation is more explicit and put all templating engines on the same level (there is no
more the concept of a "default" templating engine).
Even if the notation changed, the semantic has not. So, the logical template name for the above
examples is still 'index'. So, if you use a database loader for instance, the template
name is 'index' and everything else are options.
Upgrading current applications can be easily done by appending .php to each existing template
name reference (in both controllers and templates), and changing :twig to .twig for Twig templates
(for twig templates, you should also add .twig within templates themselves when referencing
another Twig templates).
A Controller must now implements ControllerInterface.
The BaseController can be used as the base class for Controllers.
The Controller class adds some proxy methods and an array access to the Container.