Creating a chat script with PHP and Ajax,

Introduction

In this multi-part tutorial series I will show you how to create your own chat script with PHP and Ajax. You've probably heard of Ajax before, and what it exactly is, but in case you haven't, read the following two tutorials to learn more about Ajax: "Mastering Ajax, Part 1: Introduction to Ajax" and "Getting started with Ajax".
Another JavaScript library we'll be using is the Prototype library, which includes many useful JavaScript functions and comes with inbuilt Ajax support. If you want to know more about this library, have a look at the following tutorial: "Using prototype.js v1.3.1".
In this first part of the series I will show you how to create a really basic chat script, and nothing more. In the next parts we'll be adding more features, eventually creating a really robust and powerful chat script.

How it works

Our chat script will consist of two parts: a server and a client.
The client is used by your visitors, and doesn't contain any PHP at all. The client must do all the data sending. Every time the user wants to send a new message, the client must send this data (using Ajax) to the server. The client must also check for new messages on the server, again using an Ajax request.

The server only has to add a new message or send a list of messages to the client, and it doesn't have to use any HTML or JavaScript at all. It's strictly PHP. I've added a simple diagram below to show what I've just described:

Posted by Srirajeth