Our examples to this point have focused on the task of retrieving static data files from the web server. However, the Ajax technique really comes into its own only when the server can dynamically shape the data based on input from the browser. We're helped along by jQuery in this task as well; all of the methods we've covered so far can be modified so that data transfer becomes a two-way street.
Tip
Interacting with server-side code
Since demonstrating these techniques requires interaction with the web server, we'll need to use server-side code for the first time here. The examples given will use the PHP scripting language, which is very widely used as well as freely available. We will not cover how to set up a web server with PHP here; beginners should consider a package such as XAMPP, which can be found at http://www.apachefriends.org/en/xampp.html, to get started quickly.