AJAX is a complex technique which can be a different thing for every person. For visitors, browsing AJAX made websites, this can be a very friendly experience, not different from Flash and ActionScript and for developers AJAX is Asynchronous Javascript and XML, "a new way to use existing standards".
AJAX as an inovation was launched due to a growing need to improve user experience making browsing available in less time avoiding reloads and redirections by keeping them on the same page. A big amount of time is saved using AJAX.
AJAX can also be a dangerous game for webmasters who use it too often and where it souldn't be used. For example a website made only in AJAX, basically keeping the user on the same page, will not receive bookmarks vrom the visitors because they are viewing the same url all the time and we all know how important is to offer our visitors a good way to bookmark our website.
A good example will be one when, in conjunction with PHP or other programming language, we fill out a form and click submit; normally, the javascript (client side) validation code will popup in case something is wrong but when it's not present or our visitors is keeping Javascript turned off, the page will do a redirect, validate and then print an error message causing this to either lose important POST data which also scares visitors (they have to complete the form over and over again) or lose important time which, again, scares visitors. AJAX can do this type of validation "on the spot".
AJAX can show you where you did wrong even as you type, in real time. This is a huge advantage if you ask me. There are already a lot of applications that benefit of this real time validation and processing like rating stars, live searchable grids, tooltips, ecommerce sites with drag and drop and so on.
Anyhow, AJAX is young and can be dangerous or can be vulnerable if not used securely. Ajax was "invented" in feb 2005 by Jesse James Garett in the article "Ajax: A New Approach to Web Applications".
There we have it. The good the bad and the ugly about AJAX. I can't wait to here more from this language as it sure promises much.
But why "
Building a responsive web application in ajax and php"? Where's the PHP part you would ask. I used this title to also present you a book written by Cristian Darie, Bogdan Brinzarea, Filip Chereches-Tosa, Mihai Bucica which should make your life easyer in your way to building AJAX applications that work with PHP. Here's the description from the authors:<
"
Building Responsive Web Applications with AJAX and PHP is the most practical and efficient resource a reader can get to enter the exciting world of AJAX. This book will teach you how to create faster, lighter, better web applications by using the AJAX ingredients technologies to their full potential. Assuming a basic knowledge of PHP, XML, JavaScript and MySQL, this book will help you understand how the heart of AJAX beats and how the constituent technologies work together. After teaching the foundations, the book will walk you through eight real-world case studies covering tasks you?ll be likely to need for your own applications: - AJAX enabled form-validation page - Online chat room - Customized type-ahead text entry solution, that helps users find the help page for the PHP functions - A simple cards game that supports multiple simultaneous sessions - Whiteboard where online users can draw online - Database-enabled, editable and customizable data grid - RSS aggregator application - Use the script.aculo.us JavaScript toolkit to build a drag&drop enabled sortable list The appendixes guide you through installing your working environment, using powerful tools that enable debugging, improving, and profiling your code, working with XSLT and XPath, and working with existing AJAX frameworks."
