When you initially dive into the world of Flex development, most PHP'ers will quickly notice something weird. We're out of the world of Request/Response that we know and understand and into an odd world of Events, Listeners, and Publishers/Subscribers where things just don't play well together.

He talks about the Observer design pattern and how it works to provide an interface to other objects who are listening in and waiting for events to happen (he uses an airline analogy). He also gives a more concrete illustration - uploading a file - and how the events would be used to handle each part of the process.

This article explores both of these sides ([the Publisher in Part 1 and] the Subscriber in Part 2), and introduces the basic code to get each working. The article also opens with a general introduction to this new protocol which you will definitely be hearing more about (especially if you run a blog) and contrasts it to its nearest rival, rssCloud.

He talks about the differences between it and the rssCloud functionality and gives an example of its use with the Zend_Feed_Pubsubhubbub Zend Framework component. His sample shows how to set up a publisher andn define topic and hub URLs for the service to use.