Updating the user list should occur whenever the user adds a new chat message or refreshes the chat window. Since we already use the MessageAction() method on our PHP IndexController class to forward such responses to the browser, we'll simply amend it to also return a list of currently online users.

They start by altering the MessageAction controller to handle the fetching of online users and split out the code to grab the latest messages into a getNewMessages function. They check who is online by looking at the last messages to the queue (not reliable, but about as good as it can get with a stateless protocol). Finally, they update the handleRefresh method to execute the new "find online users" code as pass it on to the output view.

In this part of the series (part 5) they show how to:

• create PDFs
• use positioning in adding text, graphics, and shapes to the document
• manage long blocks of text
• stream out a dynamic PDF to the browser
• add information to an existing PDF document

Part six picks up where the previous part left off and includes information on working with emails in the Zend Frameork. They look at the Zend_Mail component and, making some minor changes to the application they've been constructing (the feed reader). They create an email notification to the user when a feed has been updated.

Code examples and the source code for both of these sections are provided.

This series has so far focused on XML technologies and how they can be utilised using PHP 5. A subject we have not touched upon yet, is XML validation. This article will explore the application independent XML validation standards of DTD's, the XML Schema Language and the XSLT-based Schematron language.

They point back to part one of the series for the XML library they'll use and waste no time getting right into the code. They demonstrate a simple validation first before moving on to the use of DTDs to ensure the correct content. Next up is more work with the XML schemas continuing on to the Schematron functionality (their use and validation).