Facebook's real-time updates let us monitor when certain information changes about our users, and subscribing to updates helps ensure data stays current.
Design patterns standardize common solutions for the problems we face in developing complex software. One such problem is managing a complex series of actions in a workflow. The Facade pattern helps hide the complexity to expose a clean, neat API. See exactly what Facade is and how help us write good code.
Apple's Passbook is a very interesting piece of technology that involves a lot of well-known and loved tools like JSON and RESTful APIs. See how to build a sample web app that creates and distributes passes. Though the example presented isn't a full-featured product, it can serve as a nice base to build on for more serious real world uses.
Reuse templates and features in multiple places throughout your PHP code by extending Twig templates by using template inheritance, functions, and filters.