// Save stuff in the session
// Fetch them back, some other page load, some other day
$newX = Session::get('Identifier.X');
$newY = unserialize(Session::get('MyLongIdString'));
$newZ = unserialize(Session::get('ThatPage'));
// Don't really put objects like $z in session,
// it makes them way heavy and they'll chew up
// a ton of resources as they have to be loaded from
// disk every time a page is served (depending on
// your PHP session storage settings)
Thats all there really is to it. Create a unique identifier string and set/get. You will have that data persistently available until the session expires. Do make a habit of keeping it cleaned up because it can get expensive to load/save huge sessions.
Also remember to serialize/unserialize any complex objects (like anything not a string).