Check if username is being used - php

Question

I'm wondering if and how I could check if a username is being used.
I heard you can do this with jQuery but i just want something simple since I'm a beginner.
I have tried it but i can't seam to get it right. I just have it connected to a mysql database but since when a username with the same password as another account tries to logon, theres an issue, so i need this to stop people adding multiple usernames.
Here is my simple code for the registration form and the php
<form action="" method="POST">
<p><label>name : </label>
<input id="password" type="text" name="name" placeholder="name" /></p>
<p><label>User Name : </label>
<input id="username" type="text" name="username" placeholder="username" /></p>
<p><label>E-Mail : </label>
<input id="password" type="email" name="email"/></p>
<p><label>Password : </label>
<input id="password" type="password" name="password" placeholder="password" /></p>
<a class="btn" href="login.php">Login</a>
<input class="btn register" type="submit" name="submit" value="Register" />
</form>
</div>
<?php
require('connect.php');
// If the values are posted, insert them into the database.
if (isset($_POST['username']) && isset($_POST['password'])){
$username = $_POST['username'];
$email = $_POST['email'];
$password = $_POST['password'];
$name = $_POST['name'];
$query = "INSERT INTO `user` (username, password, email, name) VALUES ('$username', '$password', '$email', '$name')";
$result = mysql_query($query);
if($result){
}
}
?>

Answer 1

For starters you don't want to just rely on something like unique field for doing this, of course you will want to add that attribute to your username column within your database but above that you want to have some sort of frontal protection above it and not rely on your database throwing an error upon INSERT INTO, you're also going to want to be using mysqli for all of this and not the old version, mysql. It's vulnerable to exploitation and no longer in common practice, here's what each of your files should look like:
connect.php
<?php
$conn = mysqli_connect("localhost","username","password","database");
// Check connection
if (mysqli_connect_errno())
{
echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
?>
register.php
<form action="insertuser.php" method="POST">
Username:
<input type="text" name="username" placeholder="Username" />
<br />
Password:
<input type="password" name="password" placeholder="Password" />
<br />
Name:
<input type="text" name="name" placeholder="Name" />
<br />
Email address:
<input type="text" name="email" placeholder="Email address" />
<br /><br />
<input type="submit" value="Register" />
</form>
<?php
// If there's an error
if (isset($_GET['error'])) {
$error = $_GET['error'];
if ($error == "usernametaken") {
echo "<h4>That username is taken!</h4>";
} elseif ($error == "inserterror") {
echo "<h4>Some kind of error occured with the insert!</h4>";
} else {
echo "<h4>An error occured!</h4>";
}
echo "<br />";
}
?>
Already have an account? Login here
insertuser.php
<?php
// Stop header errors
ob_start();
// Check if form has been posted
if (isset($_POST['username'])){
// Requre database connection file
require('connect.php');
// Clean the variables preventing SQL Injection attack
$username = mysqli_real_escape_string($conn, $_POST['username']);
$email = mysqli_real_escape_string($conn, $_POST['email']);
$password = mysqli_real_escape_string($conn, $_POST['password']);
$name = mysqli_real_escape_string($conn, $_POST['name']);
// Check if the username exists
// Construct SELECT query to do this
$sql = "SELECT id FROM user WHERE username = '".$username."';";
$result = mysqli_query($conn, $sql);
$rowsreturned = mysqli_num_rows($result);
// If the username already exists
if ($rowsreturned != 0) {
echo "Username exists, redirecting to register.php with an error GET variable!";
// Redirect user
header('Location: register.php?error=usernametaken');
} else {
// Construct the INSERT INTO query
$sql = "INSERT INTO user (username, password, email, name) VALUES ('".$username."', '".$password."', '".$email."', '".$username."');";
$result = mysqli_query($conn, $sql);
if($result){
// User was inserted
echo "User inserted!";
/* DO WHATEVER YOU WANT TO DO HERE */
} else {
// There was an error inserting
echo "Error inserting, redirecting to register.php with an error GET variable!";
// Redirect user
header('Location: register.php?error=inserterror');
}
}
}
?>
Good luck with whatever you're working on and I hope this helps!
James

Answer 2

if (isset($_POST['username']) && isset($_POST['password'])){
$username = $_POST['username'];
$email = $_POST['email'];
$password = $_POST['password'];
$name = $_POST['name'];
$query = "select username from user where username = '$username'";
$res = mysql_query($query);
$rows = mysqli_num_rows($res);
if ($rows > 0) {
print 'Username already exists...';
} else {
$query = "INSERT INTO `user` (username, password, email, name) VALUES ('$username', '$password', '$email', '$name')";
$result = mysql_query($query);
if($result){
}
}
}

Answer 3

Here is another example :) , succes.
<?php
//Set empty variables.
$usernameError = $emailError = $passwordError = $nameError = $okmsg = "";
$username = $password = $email = $name = "";
if (isset($_POST['submit'])) {
//Check if empty labels form
if (empty($_POST['name'])) {
$userError = "The 'name' is required.";
echo '<script>window.location="#registrer"</script>';
} else { $name = $_POST['name']; }
if (empty($_POST['email'])) {
$emailError = "El 'Email' es requerido.";
echo '<script>window.location="#registrer"</script>';
} else {
$email = $_POST['email'];
//Check only contain letters and whitespace.
if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
$emailError = "El 'Email' is not valid. ";
echo '<script>window.location="#registrer"</script>';
}
}
if (empty($_POST['password'])) {
$passwordError = "The 'password' is requiered.";
echo '<script>window.location="#registrer"</script>';
} else {
$password = $_POST['password'];
}
}
//Check if correctly filled
if ($name && $username && $email && $password) {
require('connect.php');
//Query SQL
$sql = "SELECT * FROM user WHERE username='$username'"; //String SQL
$query = mysqli_query($ConDB, $sql);//Query
//Securite
$username = mysqli_real_escape_string($ConDB, $username);
$password = mysqli_real_escape_string($ConDB, $username);
$passw = sha1($password);//For securite.
$name = mysqli_real_escape_string($ConDB, $username);
$email = mysqli_real_escape_string($ConDB, $username);
if ($existe = mysqli_fetch_object($query)) {
$usernameError = "The 'Username' is already exists.";
echo '<script>window.location="#registrer"</script>';
} else {
$sql = "INSERT INTO user (username, password, email, name) VALUES ('$username', '$passw', '$email', '$name')";
mysqli_query($ConDB, $sql);
$okmsg = "Register with succes.";
mysqli_close($ConDB);//Close conexion.
echo '<script>window.location="#registrer"</script>';
}
}
?>
<a name="registrer"></a>
<form action="" method="POST">
<p><label>name : </label>
<input id="password" type="text" name="name" placeholder="name" /></p>
<?php echo $nameError; ?>
<p><label>User Name : </label>
<input id="username" type="text" name="username" placeholder="username" /></p>
<?php echo $usernameError; ?>
<p><label>E-Mail : </label>
<input id="password" type="email" name="email"/></p>
<?php echo $emailError; ?>
<p><label>Password : </label>
<input id="password" type="password" name="password" placeholder="password" /></p>
<?php echo $passwordError; ?>
<a class="btn" href="login.php">Login</a>
<input class="btn register" type="submit" name="submit" value="Register" />
<?php echo $okmsg; ?>
</form>
--
-- DATA BASE: `user`
--
SET SQL_MODE = "NO_AUTO_VALUE_ON_ZERO";
SET time_zone = "+00:00";
CREATE TABLE user (
id int(11) unsigned not null auto_increment primary key,
name varchar(50) not null,
email varchar(80) not null unique,
username varchar(30) not null unique,
password varchar(40) not null
)engine=InnoDB default charset=utf8 collate=utf8_general_ci;

Answer 4

You can try use jQuery AJAX for what you want.
First, add this to your registration.php file
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script>
// when user submit the form
$('form').on('submit', function(event){
$.ajax({
url: "check_username.php",
type: "POST",
dataType: "JSON",
data: {
username: $("#username").val() // get the value from username textbox
},
success: function(data){
if(data.status == "exists"){
alert('Username already existed');
}
else{
$('form').submit();
}
},
});
event.preventDefault();
});
</script>
So now your registration.php file will look like this
registration.php
<form action="" method="POST">
<p>
<label>name : </label>
<input id="password" type="text" name="name" placeholder="name" />
</p>
<p>
<label>User Name : </label>
<input id="username" type="text" name="username" placeholder="username" />
</p>
<p>
<label>E-Mail : </label>
<input id="password" type="email" name="email"/>
</p>
<p>
<label>Password : </label>
<input id="password" type="password" name="password" placeholder="password" />
</p>
<a class="btn" href="login.php">Login</a>
<input class="btn register" type="submit" name="submit" value="Register" />
</form>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script>
// when user typing in 'username' textbox
$('form').on('submit', function(event){
$.ajax({
url: "check_username.php",
type: "POST",
dataType: "JSON",
data: {
username: $("#username").val() // get the value from username textbox
},
success: function(data){
if(data.status == "exists"){
alert('Username already existed');
}
else{
$('form').submit();
}
},
});
event.preventDefault();
});
</script>
Then create php file named check_username.php to check the username submitted by user if it is already existed in database or still available.
check_username.php
<?php
// Check if 'username' textbox is not empty
if(!empty($_POST['username'])){
$username = trim(mysqli_real_escape_string($_POST['username']));
// Check the database if the username exists
$query = "SELECT username FROM `user` WHERE username = '".$username."'";
$result = mysqli_query($query);
if(mysqli_num_rows($result) > 0){
// if username already exist
// insert into array, to be sent to registration.php later
$response['status'] = 'exists';
}
else{
// if username available
$response['status'] = 'available';
}
}
header('Content-type: application/json');
echo json_encode($response);
exit;
?>
Here is how it works:
1. When user click the register button, jQuery will call check_username.php.
2. Now in check_username.php it will check the database if the username submitted already exists or still available.
3. Whatever the result either exists or available, check_username.php will send the result back to registration.php as string contains 'exists' or 'available'.
4. registration.php now get the result and will check the result sent by check_username.php if it contain 'exists' or 'available'. If the string is 'exists' then alert will be triggered. If the string is 'available', the form will be submitted.