I downloaded the LiveValidation script recently and I realised after implementing it on a webpage I did not understand how it interacts with a PHP or ASP.NET application and it got me thinking that maybe I need to just try and understand how server-side and client-side code interacts with JavaScript.

What is AJAX? I know it’s an acronym for Asynchronous JavaScript and XML, but what does it really mean and how does it work. Client- and Server-side scripting is easy to understand on their own and its easy to understand how both technologies are used, but where it becomes tricky for myself is when the server-side and client-side code need to interact with each other. Developing web applications with ASP.NET does not always expose a developer to the inner workings of that specific technology. AJAX is not unique to PHP or ASP.NET. Both ASP.NET and PHP are server side scripting languages. The first thing to understand is that AJAX is not a technology on its own, nor is it something that has not been there before, because it uses existing technologies (JavaScript, XML) to do what it does. AJAX uses a combination of programming tools to create web-based applications that react more like software applications – this means that the web-based application responds much smoother and nicer and the page does not reload to retrieve new content.

I still have not defined what AJAX looks like or what it exactly does. AJAX is based on open standards such as HTML, CSS, XML and JavaScript. AJAX uses XML and HTTP Requests to communicate with a web server. Another important thing to note is that with AJAX web applications do not re-submit a web page every time a user makes a request. If for example a user enters data on a form and submits the information to a web server, the web server will traditionally create a new page after the submit has occurred, but AJAX communicates with the web server in such a way that updates to the page only happen to the sections of the page that are affected.