Custom keys in $_SESSION are deprecated

Custom session values stored directly in the $_SESSION super global are deprecated. Instead access session attributes via $request->getSession()->set() and $request->getSession->get().

Deprecated:

Set a value in the session

$_SESSION['test_key'] = 'test_value';

Get a value from the session

$value = $_SESSION['test_key'] ?? 'default_value';

Recommended:

Set a value in the session

$request->getSession()->set('test_key', 'test_value');

Get a value from the session

$value = $request->getSession()->get('test_key', 'default_value');