Nos mandan un artículo de como implementar una aplicación tipo Twitter usando PHP:
Learn how to use PHP to add a Twitter-like interface to your applications. Specifically, we show you how to allow users to add posts, disseminate those posts to other users who want to receive them, and allow users to choose to follow the posts of other users. With any luck, you can take what you will learn here, add it to your application, and tailor it to your needs.