How To Create Database-enabled Ajax Requests Using PHP and MySQL

We know that Ajax is one of the hottest things in the world of web and has certainly given the field a new dimension. If Ajax has to compete with desktop applications then database interaction is absolutely required.
While searching the internet I came across an interesting article regarding how database enabled Ajax requests could be created using PHP and MySQL. To start with front end HTML and JavaScript files have to be created for making requests to the server side. What we get is a PHP file which fills the vacuum between Ajax and PHP object connecting to a MySQL database and returning results as an XML response to the Ajax engine.