The Stream PHP SDK by Stream allows API interaction to access activity streams and news feeds data. Installation with composer is available. Usage demonstrates how to create a new client, set API endpoint, and create a new feed activity.
There are a number of ways of delivering data in real-time but until recently it has looked like PubSubHubbub, with the backing of Google, was going to be the preferred method. However, the past couple of weeks have seen a couple of interesting developments which could indicate that the developer community may actually prefer HTTP Streaming.