Integrating with Legacy Sessions

Sometimes it may be necessary to integrate Symfony into a legacy application where you do not initially have the level of control you require.

As stated elsewhere, Symfony Sessions are designed to replace the use of PHP's native session_*() functions and use of the $_SESSION superglobal. Additionally, it is mandatory for Symfony to start the session.

However, when there really are circumstances where this is not possible, you can use a special storage bridge PhpBridgeSessionStorage which is designed to allow Symfony to work with a session started outside of the Symfony HttpFoundation component. You are warned that things can interrupt this use-case unless you are careful: for example the legacy application erases $_SESSION.

A typical use of this might look like this:

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use Symfony\Component\HttpFoundation\Session\Session;
use Symfony\Component\HttpFoundation\Session\Storage\PhpBridgeSessionStorage;

// legacy application configures session
ini_set('session.save_handler', 'files');
ini_set('session.save_path', '/tmp');
session_start();

// Get Symfony to interface with this existing session
$session = new Session(new PhpBridgeSessionStorage());

// symfony will now interface with the existing PHP session
$session->start();

This will allow you to start using the Symfony Session API and allow migration of your application to Symfony sessions.