How to check already exist username when user input on Sig Up Form

What Will I Learn?

Write here briefly the details of what the user is going to learn in a bullet list.

You will learn how to get data from html element
You will learn how send data using ajax
You will learn on input event in jQuery
You will learn how to execute SQL query using PHP and AJAX

Requirements

Basic knowledge about HTML
Basic knowledge about JavaScript
Basic knowledge about PHP
Basic knowledge about MySql
You have to install or host the jQuery file, You can add jQuery CDN if you don't want to install or host it
To practice this tutorial you should have a webserver, text editor and a browser. In this tutorial I use XAMPP for webserver, Visual Studio Code for text editor and Google Crome for browser.

Difficulty

Intermediate

Tutorial Contents

On a website, the username of one account and other accounts should not be the same.to solve this problem, it is necessary to check the process when the user to register. In this tutorial we will create a checking process whether the filled username already exists or not. This process is automatic when the user inputs. If the username is already entered it will issue an error message and vice versa. For more detail lets pay attention steps bellow :

$activate webserver

ReActive your webserver. create new folder in Xampp/htdocs/ if you use XAMPP. While you use Linux create it at var/www.

$Creating Database

Open phpmyadmin if you use XAMPP to create a new database. Or open your sql then create new database.

CREATE DATABASE SIGUP;

Create a sample user table

CREATE TABLE `sigup`.`user` ( `id` SMALLINT NOT NULL AUTO_INCREMENT , `username` VARCHAR(30) NOT NULL , `password` VARCHAR(30) NOT NULL , PRIMARY KEY (`id`)) ENGINE = InnoDB;

INSERT some data for example, username and password

INSERT INTO `user` (`id`, `username`, `password`) VALUES (NULL, 'utopian', 'utopian'), (NULL, 'dsound', 'dsound'), (NULL, 'dmania', 'dmania'), (NULL, 'dtube', 'dtube'), (NULL, 'esteem', 'esteem')

$Creating a simple username input in HTML sigup Form

Open your text editor software, Create new file and save as sigup.html in the previous folder that created by you.
Add the HTML element as usual.

<html>
<head>
<title>Check username</title>
</head>
<body>
</body>
</html>

Creata a simple input text

Username : <input id="uname" type="text">

Add a <span> element to display alert message

<span id="alert"></span>

$Adding jQuery AJAX

As we know, to use jQuery we need to install or host it. Or we can also add jQuery CDN if we don't want to install or host it. we also have many choices CDN that we can use, either Google CDN or Microsoft CDN. For more Detail you can visit jquery official web. In this tutorial I use Google CDN. Add the CDN in <head> element.

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>

To write the jQuery Script we should open <script> tag. You can put it in <head> element or in <body> element.

<script></script>

Before add more event in jQuery. There is an event that we should add for the first. It is ready() event. this event to make sure that all html elements are loaded. if it is, then it will load jQuery script. So, all jQuery Script must write in this function event.

$(document).ready(function(){
});

Select the username input and add on input event function

 $("#uname").on("input", function(){
});

Get data from input and save it to variable. To get data when inputing we can use $(this)

var uname=$(this).val();

Check username length. Here we make the condition if the username input < 3 will say so short. And will process in input > 3.

if(uname.length < 3){
                    $("#alert").text("so short");
                }

Create else condition

else{
}

to check data in database add the ajax function in else condition.

$.ajax({
                        url:'check.php',
                        method:'POST',
                        data:{
                            username:uname
                        },
                        success:function(response){
                            $("#alert").text(response);
                        }
                    });

Explanation Script : url:'check.php', url address that will send the data. method:'POST', sending method. data:{username:uname }, getting data from JS variabel. success:function(response) the function that will be execute if Ajax success, the response is the parameter to get back data from check.php. $("#alert").text(response); set text for span with id=alert with the data that send from php file

$Create The PHP file

Create new file on your text editor application and save as check.php [the url that you mention on AJAX function].
Open MySql connection.

$conn = new mysqli('localhost', 'root', '', 'sigup');

Add the variable to accommodate data that send from the FORM by method POST

$user=$_POST['username'];

Add the sql Query to check data is already exist on database

$sql="SELECT * FROM user where username='$user'";

Execute the sql query

$result = $conn->query($sql);

Create a condition to check if the the username exist or not

if ($result->num_rows > 0) {
    echo "Username Already Exist";
}
else{
    echo 'Available';
}

&Testing

Save all file and try to run sigup.html on your localhost.
Try to input less then 3 character. You will get message "so short"
In database we already has user : utopian, dtube, dmania, dsound, esteem. Try to input except the the username mentioned
Try to input same with the username already exist

$full code

sigup.html

<html>
<head>
    <title>Check username</title>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
</head>
<body>
    Username : <input id="uname" type="text"> 
    <span id="alert"></span>  
    <script>
        $(document).ready(function(){
            $("#uname").on("input", function(){
                var uname=$(this).val();
                if(uname.length < 3){
                    $("#alert").text("so short");
                }
                else{
                    $.ajax({
                        url:'check.php',
                        method:'POST',
                        data:{
                            username:uname
                        },
                        success:function(response){
                            $("#alert").text(response);
                        }
                    });
                }
            });
        });
    </script> 
</body>
</html>

check.php

<?php
$conn = new mysqli('localhost', 'root', '', 'sigup');
$user=$_POST['username'];
$sql="SELECT * FROM user where username='$user'";
$result = $conn->query($sql);
if ($result->num_rows > 0) {
    echo "Username Already Exist";
}
else{
    echo 'Available';
}
?>

Downoad file on GDRIVE

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