In this chapter, you learned how to create a full-fledged Ajax application called AjaxMail. You began by designing the server-side architecture. Using PHP and MySQL, you designed a back-end system designed to download messages from a POP3 server and store them in a database. You created several database tables to handle the various data associated with an e-mail application. POP3Lib was used for POP3 communication and PHPMailer was used for SMTP communication.
You then designed a dynamic user interface that doesn't require any page reloads. Communication is accomplished by using a combination of XMLHttp and a hidden iframe. The XMHttp requests performed actions such as deleting specific e-mail message, whereas the hidden iframe was used to allow the Back and Forward buttons to function as usual.