AJAX Introduction

From http://www.w3schools.com (Copyright Refsnes Data)

# AJAX Introduction

## AJAX = Asynchronous JavaScript And XML

AJAX is an acronym for Asynchronous JavaScript And XML.

AJAX is not a new programming language, but simply a new technique for creating better, faster, and more interactive web applications.

AJAX uses JavaScript to send and receive data between a web browser and a web server.

The AJAX technique makes web pages more responsive by exchanging data with the web server behind the scenes, instead of reloading an entire web page each time a user makes a change.

## AJAX Is Based On Open Standards

AJAX is based on the following open standards:

- JavaScript
- XML
- HTML
- CSS

The open standards used in AJAX are well defined, and supported by all major browsers. AJAX applications are browser and platform independent. (Cross-Platform, Cross-Browser technology)

## AJAX Is About Better Internet Applications

Web applications have many benefits over desktop applications:

- they can reach a larger audience
- they are easier to install and support
- they are easier to develop

However, Internet applications are not always as "rich" and user-friendly as traditional desktop applications.

With AJAX, Internet applications can be made richer (smaller, faster, and easier to use).

## You Can Start Using AJAX Today

There is nothing new to learn.

AJAX is based on open standards. These standards have been used by most developers for several years.

Most existing web applications can be rewritten to use AJAX technology instead of traditional HTML forms.

## AJAX Uses XML And HTTP Requests

A traditional web application will submit input (using an HTML form) to a web server. After the web server has processed the data, it will return a completely new web page to the user.

Because the server returns a new web page each time the user submits input, traditional web applications often run slowly and tend to be less user friendly.

With AJAX, web applications can send and retrieve data without reloading the whole web page. This is done by sending HTTP requests to the server (behind the scenes), and by modifying only parts of the web page using JavaScript when the server returns data.

XML is commonly used as the format for receiving server data, although any format, including plain text, can be used.

You will learn more about how this is done in the next chapters of this tutorial.

## PHP and AJAX

There is no such thing as an AJAX server.

AJAX is a technology that runs in your browser. It uses asynchronous data transfer (HTTP requests) between the browser and the web server, allowing web pages to request small bits of information from the server instead of whole pages.

AJAX is a web browser technology independent of web server software.

However, in this tutorial we will focus more on actual examples running on a PHP server, and less on how AJAX works.

To read more about how AJAX works, visit our AJAX tutorial.

From http://www.w3schools.com (Copyright Refsnes Data)