This detailed guide covers the creation of connections to a MySQL database with PHP 5 via a custom Ajax engine and shows how to gracefully format the response with CSS, JavaScript, and XHTML while keeping the data tightly secure. It also covers the use of four custom Ajax-enabled components in an application and how to create each of them from scratch.
Hope this helps its taken from the amazons review
And
you should try to find out things for yourself since this is a fast paced world and while waiting for answers you will think of more questions