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How to Create a Simple Web-Based Chat Application

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Difficulty:BeginnerLength:LongLanguages:

In this tutorial, we will be creating a simple web-based chat application with PHP and jQuery. This sort of utility would be perfect for a live support system for your website.

This tutorial was updated recently to make improvements in the chat app. 

Introduction

TutsPlus Chat App
The chat application we will be building today will be quite simple. It will include a login and logout system, AJAX-style features, and support for multiple users.

Step 1: HTML Markup

We will start this tutorial by creating our first file, called index.php.

  • We start our HTML with the usual DOCTYPE, html, head, and body tags. In the head tag, we add our title and link to our CSS stylesheet (style.css).
  • Inside the body tag, we structure our layout inside the #wrapper div. We will have three main blocks: a simple menu, our chatbox, and our message input, each with its respective div and id.
    • The #menu div will consist of two paragraph elements. The first will be a welcome to the user and will be on the left, and the second will be an exit link and will be on the right. We are using flexbox for layout instead of floating elements.
    • The #chatbox div will contain our chatlog. We will load our log from an external file using jQuery's ajax request.
    • The last item in our #wrapper div will be our form, which will include a text input for the user message and a submit button.
  • We add our scripts last to load the page faster. We will first link to the Cloudflare jQuery CDN, as we will be using the jQuery library for this tutorial. Our second script tag is what we will be working on. We will load all of our code after the document is ready.

Step 2: CSS Styling

We will now add some CSS to make our chat application look better than with the default browser styling. The code below will be added to our style.css file.

There's nothing special about the above CSS other than the fact that some ids or classes, which we have set a style for, will be added a bit later.

TutsPlus Chat App Interface
 
As you can see above, we are finished building the chat's user interface.

Step 3: Using PHP to Create a Login Form

Now we will implement a simple form that will ask the user their name before continuing further.

The loginForm() function we created is composed of a simple login form which asks the user for his/her name. We then use an if and else statement to verify that the person entered a name. If the person entered a name, we set that name as $_SESSION['name']. Since we are using a cookie-based session to store the name, we must call session_start() before anything is outputted to the browser.

One thing that you may want to pay close attention to is that we have used the htmlspecialchars() function, which converts special characters to HTML entities, therefore protecting the name variable from falling victim to cross-site scripting (XSS). Later, we will also add this function to the text variable that will be posted to the chat log.

Showing the Login Form

In order to show the login form in case a user has not logged in, and hence has not created a session, we use another if and else statement around the #wrapper div and script tags in our original code. In the opposite case, this will hide the login form and show the chat box if the user is logged in and has created a session.

TutsPlus Chat App Login Screen

Welcome and Logout Menu

We are not yet finished creating the login system for this chat application. We still need to allow the user to log out and end the chat session. If you can remember, our original HTML markup included a simple menu. Let's go back and add some PHP code that will give the menu more functionality.

First of all, let's add the user's name to the welcome message. We do this by outputting the session of the user's name.

Tutsplus Chat App Welcome

In order to allow the user to log out and end the session, we will jump ahead of ourselves and briefly use jQuery.

The jQuery code above simply shows a confirmation alert if a user clicks the #exit link. If the user confirms the exit, therefore deciding to end the session, then we send them to index.php?logout=true. This simply creates a variable called logout with the value of true. We need to catch this variable with PHP:

Tutsplus Chat APp Logout Prompt

We now see if a get variable of 'logout' exists using the isset() function. If the variable has been passed via a URL, such as the link mentioned above, we proceed to end the session of the user's name.

Before destroying the user's name session with the session_destroy() function, we want to write a simple exit message to the chat log. It will say that the user has left the chat session. We do this by using the file_put_contents() function to manipulate our log.html file, which, as we will see later on, will be created as our chat log. The file_put_contents() function is a convenient way to write data to a text file instead of using fopen()fwrite(), and fclose() each time. Just make sure that you pass appropriate flags like FILE_APPEND to append the data at the end of the file. Otherwise, a new $logout_message will overwrite the previous content of the file. Please note that we have added a class of msgln to the div. We have already defined the CSS styling for this div.

After doing this, we destroy the session and redirect the user to the same page where the login form will appear.

Step 4: Handling User Input

After a user submits our form, we want to grab their input and write it to our chat log. In order to do this, we must use jQuery and PHP to work synchronously on the client and server sides.

jQuery

Almost everything we are going to do with jQuery to handle our data will revolve around the jQuery post request.

  1. Before we do anything, we must grab the user's input, or what the user has typed into the #submitmsg input. This can be achieved with the val() function, which gets the value set in a form field. We now store this value in the clientmsg variable.
  2. Here comes our most important part: the jQuery post request. This sends a POST request to the post.php file that we will create in a moment. It posts the client's input, or what has been saved into the clientmsg variable.
  3. Lastly, we clear the #usermsg input by setting the value attribute to blank.

Please note that the code above will go into our script tag, where we placed the jQuery logout code.

PHP: The post.php File

At the moment, we have POST data being sent to the post.php file each time the user submits the form and sends a new message. Our goal now is to grab this data and write it into our chat log.

Before we do anything, we have to start the post.php file with the session_start() function as we will be using the session of the user's name in this file.

Using the isset boolean, we check if the session for 'name' exists before doing anything else. We now grab the POST data that was being sent to this file by jQuery. We store this data into the $text variable. This data, like all the overall user input data, will be stored in the log.html file. We simply use the file_put_contents() function to write all the data to the file.

The message we will be writing will be enclosed inside the .msgln div. It will contain the date and time generated by the date() function, the session of the user's name, and the text, which is also surrounded by the htmlspecialchars() function to prevent XSS.

Step 5: Displaying the Chat Log Contents

Everything the user has posted is handled and posted using jQuery; it is written to the chat log with PHP. The only thing left to do is to display the updated chat log to the user with log.php.

In order to save ourselves some time, we will preload the chat log into the #chatbox div if it has any content.

We use a similar routine as we used in the post.php file, except this time we are only reading and outputting the contents of the file.

The jQuery.ajax Request

The AJAX request is the core of everything we are doing. This request not only allows us to send and receive data through the form without refreshing the page, but it also allows us to handle the data requested.

We wrap our AJAX request inside a function. You will see why in a second. As you see above, we will only use three of the jQuery AJAX request objects.

  • url: A string of the URL to request. We will use our chat log's filename of log.html.
  • cache: This will prevent our file from being cached. It will ensure that we get an updated chat log every time we send a request.
  • success: This will allow us to attach a function that will pass the data we requested.

As you see, we then move the HTML data we requested into the #chatbox div.

Auto-Scrolling

As you may have seen in other chat applications, the content automatically scrolls down if the chat log container (#chatbox) overflows. We are going to implement a simple and similar feature, which will compare the container's scroll height before and after we do the AJAX request. If the scroll height is greater after the request, we will use jQuery's animate effect to scroll the #chatbox div.

We first store the #chatbox div's scroll height into the oldscrollHeight variable before we make the request. After our request has returned successfully, we store the #chatbox div's scrolled height into the newscrollHeight variable.

We then compare both of the scroll height variables using an if statement. If newscrollHeight is greater than the oldscrollHeight, we use the animate effect to scroll the #chatbox div.

Continuously Updating the Chat Log

Now one question may arise: how will we constantly update the new data being sent back and forth between users? Or to rephrase the question, how will we keep continuously sending requests to update the data?

The answer to our question lies in the setInterval function. This function will run our loadLog() function every 2.5 seconds, and the loadLog function will request the updated file and autoscroll the div.

Tutsplus Chat App Network

Complete Code

The chat app might not work properly for you if the right code is not placed inside the right files and in the right order. To avoid any confusion, I am posting the whole code that will go into two separate files called index.php and post.php.

Here is the code for index.php:

Here is the code for post.php:

The code that goes into style.css is already available in Step 2 of the tutorial.

If the code you have does not seem to be working, make sure it matches the code provided here. Please note that all three files—index.phppost.php, and style.css—are located in the same directory.

Finished

We are finished! I hope that you learned how a basic chat system works, and if you have any suggestions on anything, I'll happily welcome them. This chat system is a simple as you can get with a chat application. You can work off this and build multiple chat rooms, add an administrative back end, add emoticons, etc. The sky is the limit!

Also, if you need a professional app or plugin for your next project, you can take a look at one of the many Chat Scripts we have for sale on CodeCanyon.

Below are a few links you might want to check out if you are thinking of expanding this chat application:

Tutsplus Chat App

This post has been updated with contributions from Monty Shokeen. Monty is a full-stack developer who also loves to write tutorials, and to learn about new JavaScript libraries.

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