XML is the acronym for Extensible Markup Language. It is used to encode messages in both human and machine readable formats. It’s like HTML but allows you to create your custom tags. For more details on XML, see the article on XML

Why use AJAX?

It allows developing rich interactive web applications just like desktop applications. Validation can be performed done as the user fills in a form without submitting it. This can be achieved using auto completion. The words that the user types in are submitted to the server for processing. The server responds with keywords that match what the user entered. It can be used to populate a dropdown box depending on the value of another dropdown box Data can be retrieved from the server and only a certain part of a page updated without loading the whole page. This is very useful for web page parts that load things like Tweets Commens Users visiting the site etc.

How to Create an PHP Ajax application

We will create a simple application that allows users to search for popular PHP MVC frameworks. Our application will have a text box that users will type in the names of the framework. We will then use mvc AJAX to search for a match then display the framework’s complete name just below the search form.

Step 1) Creating the index page

Index.php HERE,

“onkeyup=”showName(this.value)”” executes the JavaScript function showName everytime a key is typed in the textbox. This feature is called auto complete

Step 2) Creating the frameworks page

frameworks.php

Step 3) Creating the JS script

auto_complete.js HERE,

	“if (str.length == 0)” check the length of the string. If it is 0, then the rest of the script is not executed.

	“if (window.XMLHttpRequest)…” Internet Explorer versions 5 and 6 use ActiveXObject for AJAX implementation. Other versions and browsers such as Chrome, FireFox use XMLHttpRequest. This code will ensure that our application works in both IE 5 & 6 and other high versions of IE and browsers.

	“xmlhttp.onreadystatechange=function…” checks if the AJAX interaction is complete and the status is 200 then updates the txtName span with the returned results.

Step 4) Testing our PHP Ajax application

Assuming you have saved the file index.php In phututs/ajax, browse to the URL http://localhost/phptuts/ajax/index.php

Type the letter C in the text box You will get the following results.

The above example demonstrates the concept of AJAX and how it can help us create rich interaction applications.

Summary

	AJAX is the acronym for Asynchronous JavaScript and XML

	AJAX is a technology used to create rich interaction applications that reduce the interactions between the client and the server by updating only parts of the web page.

	Internet Explorer version 5 and 6 use ActiveXObject to implement AJAX operations.

	Internet explorer version 7 and above and browsers Chrome, Firefox, Opera, and Safari use XMLHttpRequest.