Suppose we have an article page on our site where people can edit articles. The article has an edit and save button which allows the user to edit the article and save the changes as necessary. View the ajax_edit_in_place demo to see what I'm talking about.

They've gone with Prototype to handle the AJAX connection and provide both the Javascript and PHP code for editing, saving and canceling an edit on the page's content.

Edit in place, like many other Ajax functions, uses the XmlHttpRequest Object to call an external page to send and receive information.

They start with the planning, the layout of how the mini application would work before even getting into the code. They assume that you already know how to work with a MySQL database and have an abstraction layer in place before starting in with the Javascript - echoing out the records (print_records), switching from a div to a textarea (changeClass), putting the content back into the database (save), and updating the page with the new information (update_page).

By the end you're left with a simple, clean edit-in-place that you can drop into any page that uses divs to contain the content.