PHP MySQL Login System
Implementing User Authentication Mechanism
User authentication is essential in modern web applications as a security measure to restrict unauthorized access to member-only areas and tools on a site.
In this tutorial, we'll develop a simple registration and login system using PHP and MySQL. The tutorial consists of two main parts: first, we'll create a user registration form, and second, we'll create a login form along with a welcome page and logout script.
Building the Registration System
In this section, we'll create a registration system that enables users to create a new account by filling out a web form. However, first we need to create a table to store all user data.
Step 1: Creating the Database Table
Run the following SQL query to create the users table in your MySQL database.
CREATE TABLE users (
id INT NOT NULL PRIMARY KEY AUTO_INCREMENT,
username VARCHAR(50) NOT NULL UNIQUE,
password VARCHAR(255) NOT NULL,
created_at DATETIME DEFAULT CURRENT_TIMESTAMP
);
For detailed information about the syntax for creating tables in the MySQL database system, please refer to the tutorial on SQL CREATE TABLE statement.
Step 2: Creating the Config File
After creating the table, we need to create a PHP script to connect to the MySQL database server. Let's create a file named "config.php" and insert the following code into it.
Example
Procedural Object Oriented PDO
Download
<?php
/* Database credentials. Assuming you are running MySQL
server with default setting (user 'root' with no password) */
define('DB_SERVER', 'localhost');
define('DB_USERNAME', 'root');
define('DB_PASSWORD', '');
define('DB_NAME', 'demo');
/* Attempt to connect to MySQL database */
$link = mysqli_connect(DB_SERVER, DB_USERNAME, DB_PASSWORD, DB_NAME);
// Check connection
if($link === false){
die("ERROR: Could not connect. " . mysqli_connect_error());
}
?>
<?php
/* Database credentials. Assuming you are running MySQL
server with default setting (user 'root' with no password) */
define('DB_SERVER', 'localhost');
define('DB_USERNAME', 'root');
define('DB_PASSWORD', '');
define('DB_NAME', 'demo');
/* Attempt to connect to MySQL database */
$mysqli = new mysqli(DB_SERVER, DB_USERNAME, DB_PASSWORD, DB_NAME);
// Check connection
if($mysqli === false){
die("ERROR: Could not connect. " . $mysqli->connect_error);
}
?>
<?php
/* Database credentials. Assuming you are running MySQL
server with default setting (user 'root' with no password) */
define('DB_SERVER', 'localhost');
define('DB_USERNAME', 'root');
define('DB_PASSWORD', '');
define('DB_NAME', 'demo');
/* Attempt to connect to MySQL database */
try{
$pdo = new PDO("mysql:host=" . DB_SERVER . ";dbname=" . DB_NAME, DB_USERNAME, DB_PASSWORD);
// Set the PDO error mode to exception
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch(PDOException $e){
die("ERROR: Could not connect. " . $e->getMessage());
}
?>
If you've downloaded the Object Oriented or PDO code examples using the download button, please delete the text "-oo-format" or "-pdo-format" from the file names before testing the code.
Note: Before testing this code, make sure to replace the credentials with your MySQL server settings. For example, replace the database name 'demo' with your own database name, change the username 'root' to your database username, and specify a database password if required.
Step 3: Creating the Registration Form
Next, let's create another PHP file named "register.php" and insert the following example code into it. This code will create a web form that allows users to register.
This script will also display errors if a user attempts to submit the form without entering any values, or if the username entered is already taken by another user.
Example
Procedural Object Oriented PDO
Download
<?php
// Include config file
require_once "config.php";
// Define variables and initialize with empty values
$username = $password = $confirm_password = "";
$username_err = $password_err = $confirm_password_err = "";
// Processing form data when form is submitted
if($_SERVER["REQUEST_METHOD"] == "POST"){
// Validate username
if(empty(trim($_POST["username"]))){
$username_err = "Please enter a username.";
} elseif(!preg_match('/^[a-zA-Z0-9_]+$/', trim($_POST["username"]))){
$username_err = "Username can only contain letters, numbers, and underscores.";
} else{
// Prepare a select statement
$sql = "SELECT id FROM users WHERE username = ?";
if($stmt = mysqli_prepare($link, $sql)){
// Bind variables to the prepared statement as parameters
mysqli_stmt_bind_param($stmt, "s", $param_username);
// Set parameters
$param_username = trim($_POST["username"]);
// Attempt to execute the prepared statement
if(mysqli_stmt_execute($stmt)){
/* store result */
mysqli_stmt_store_result($stmt);
if(mysqli_stmt_num_rows($stmt) == 1){
$username_err = "This username is already taken.";
} else{
$username = trim($_POST["username"]);
}
} else{
echo "Oops! Something went wrong. Please try again later.";
}
// Close statement
mysqli_stmt_close($stmt);
}
}
// Validate password
if(empty(trim($_POST["password"]))){
$password_err = "Please enter a password.";
} elseif(strlen(trim($_POST["password"])) < 6){
$password_err = "Password must have atleast 6 characters.";
} else{
$password = trim($_POST["password"]);
}
// Validate confirm password
if(empty(trim($_POST["confirm_password"]))){
$confirm_password_err = "Please confirm password.";
} else{
$confirm_password = trim($_POST["confirm_password"]);
if(empty($password_err) && ($password != $confirm_password)){
$confirm_password_err = "Password did not match.";
}
}
// Check input errors before inserting in database
if(empty($username_err) && empty($password_err) && empty($confirm_password_err)){
// Prepare an insert statement
$sql = "INSERT INTO users (username, password) VALUES (?, ?)";
if($stmt = mysqli_prepare($link, $sql)){
// Bind variables to the prepared statement as parameters
mysqli_stmt_bind_param($stmt, "ss", $param_username, $param_password);
// Set parameters
$param_username = $username;
$param_password = password_hash($password, PASSWORD_DEFAULT); // Creates a password hash
// Attempt to execute the prepared statement
if(mysqli_stmt_execute($stmt)){
// Redirect to login page
header("location: login.php");
} else{
echo "Oops! Something went wrong. Please try again later.";
}
// Close statement
mysqli_stmt_close($stmt);
}
}
// Close connection
mysqli_close($link);
}
?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Sign Up</title>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css">
<style>
body{ font: 14px sans-serif; }
.wrapper{ width: 360px; padding: 20px; }
</style>
</head>
<body>
<div class="wrapper">
<h2>Sign Up</h2>
<p>Please fill this form to create an account.</p>
<form action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]); ?>" method="post">
<div class="form-group">
<label>Username</label>
<input type="text" name="username" class="form-control <?php echo (!empty($username_err)) ? 'is-invalid' : ''; ?>" value="<?php echo $username; ?>">
<span class="invalid-feedback"><?php echo $username_err; ?></span>
</div>
<div class="form-group">
<label>Password</label>
<input type="password" name="password" class="form-control <?php echo (!empty($password_err)) ? 'is-invalid' : ''; ?>" value="<?php echo $password; ?>">
<span class="invalid-feedback"><?php echo $password_err; ?></span>
</div>
<div class="form-group">
<label>Confirm Password</label>
<input type="password" name="confirm_password" class="form-control <?php echo (!empty($confirm_password_err)) ? 'is-invalid' : ''; ?>" value="<?php echo $confirm_password; ?>">
<span class="invalid-feedback"><?php echo $confirm_password_err; ?></span>
</div>
<div class="form-group">
<input type="submit" class="btn btn-primary" value="Submit">
<input type="reset" class="btn btn-secondary ml-2" value="Reset">
</div>
<p>Already have an account? <a href="login.php">Login here</a>.</p>
</form>
</div>
</body>
</html>
<?php
// Include config file
require_once "config.php";
// Define variables and initialize with empty values
$username = $password = $confirm_password = "";
$username_err = $password_err = $confirm_password_err = "";
// Processing form data when form is submitted
if($_SERVER["REQUEST_METHOD"] == "POST"){
// Validate username
if(empty(trim($_POST["username"]))){
$username_err = "Please enter a username.";
} elseif(!preg_match('/^[a-zA-Z0-9_]+$/', trim($_POST["username"]))){
$username_err = "Username can only contain letters, numbers, and underscores.";
} else{
// Prepare a select statement
$sql = "SELECT id FROM users WHERE username = ?";
if($stmt = $mysqli->prepare($sql)){
// Bind variables to the prepared statement as parameters
$stmt->bind_param("s", $param_username);
// Set parameters
$param_username = trim($_POST["username"]);
// Attempt to execute the prepared statement
if($stmt->execute()){
// store result
$stmt->store_result();
if($stmt->num_rows == 1){
$username_err = "This username is already taken.";
} else{
$username = trim($_POST["username"]);
}
} else{
echo "Oops! Something went wrong. Please try again later.";
}
// Close statement
$stmt->close();
}
}
// Validate password
if(empty(trim($_POST["password"]))){
$password_err = "Please enter a password.";
} elseif(strlen(trim($_POST["password"])) < 6){
$password_err = "Password must have atleast 6 characters.";
} else{
$password = trim($_POST["password"]);
}
// Validate confirm password
if(empty(trim($_POST["confirm_password"]))){
$confirm_password_err = "Please confirm password.";
} else{
$confirm_password = trim($_POST["confirm_password"]);
if(empty($password_err) && ($password != $confirm_password)){
$confirm_password_err = "Password did not match.";
}
}
// Check input errors before inserting in database
if(empty($username_err) && empty($password_err) && empty($confirm_password_err)){
// Prepare an insert statement
$sql = "INSERT INTO users (username, password) VALUES (?, ?)";
if($stmt = $mysqli->prepare($sql)){
// Bind variables to the prepared statement as parameters
$stmt->bind_param("ss", $param_username, $param_password);
// Set parameters
$param_username = $username;
$param_password = password_hash($password, PASSWORD_DEFAULT); // Creates a password hash
// Attempt to execute the prepared statement
if($stmt->execute()){
// Redirect to login page
header("location: login.php");
} else{
echo "Oops! Something went wrong. Please try again later.";
}
// Close statement
$stmt->close();
}
}
// Close connection
$mysqli->close();
}
?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Sign Up</title>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css">
<style>
body{ font: 14px sans-serif; }
.wrapper{ width: 360px; padding: 20px; }
</style>
</head>
<body>
<div class="wrapper">
<h2>Sign Up</h2>
<p>Please fill this form to create an account.</p>
<form action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]); ?>" method="post">
<div class="form-group">
<label>Username</label>
<input type="text" name="username" class="form-control <?php echo (!empty($username_err)) ? 'is-invalid' : ''; ?>" value="<?php echo $username; ?>">
<span class="invalid-feedback"><?php echo $username_err; ?></span>
</div>
<div class="form-group">
<label>Password</label>
<input type="password" name="password" class="form-control <?php echo (!empty($password_err)) ? 'is-invalid' : ''; ?>" value="<?php echo $password; ?>">
<span class="invalid-feedback"><?php echo $password_err; ?></span>
</div>
<div class="form-group">
<label>Confirm Password</label>
<input type="password" name="confirm_password" class="form-control <?php echo (!empty($confirm_password_err)) ? 'is-invalid' : ''; ?>" value="<?php echo $confirm_password; ?>">
<span class="invalid-feedback"><?php echo $confirm_password_err; ?></span>
</div>
<div class="form-group">
<input type="submit" class="btn btn-primary" value="Submit">
<input type="reset" class="btn btn-secondary ml-2" value="Reset">
</div>
<p>Already have an account? <a href="login.php">Login here</a>.</p>
</form>
</div>
</body>
</html>
<?php
// Include config file
require_once "config.php";
// Define variables and initialize with empty values
$username = $password = $confirm_password = "";
$username_err = $password_err = $confirm_password_err = "";
// Processing form data when form is submitted
if($_SERVER["REQUEST_METHOD"] == "POST"){
// Validate username
if(empty(trim($_POST["username"]))){
$username_err = "Please enter a username.";
} elseif(!preg_match('/^[a-zA-Z0-9_]+$/', trim($_POST["username"]))){
$username_err = "Username can only contain letters, numbers, and underscores.";
} else{
// Prepare a select statement
$sql = "SELECT id FROM users WHERE username = :username";
if($stmt = $pdo->prepare($sql)){
// Bind variables to the prepared statement as parameters
$stmt->bindParam(":username", $param_username, PDO::PARAM_STR);
// Set parameters
$param_username = trim($_POST["username"]);
// Attempt to execute the prepared statement
if($stmt->execute()){
if($stmt->rowCount() == 1){
$username_err = "This username is already taken.";
} else{
$username = trim($_POST["username"]);
}
} else{
echo "Oops! Something went wrong. Please try again later.";
}
// Close statement
unset($stmt);
}
}
// Validate password
if(empty(trim($_POST["password"]))){
$password_err = "Please enter a password.";
} elseif(strlen(trim($_POST["password"])) < 6){
$password_err = "Password must have atleast 6 characters.";
} else{
$password = trim($_POST["password"]);
}
// Validate confirm password
if(empty(trim($_POST["confirm_password"]))){
$confirm_password_err = "Please confirm password.";
} else{
$confirm_password = trim($_POST["confirm_password"]);
if(empty($password_err) && ($password != $confirm_password)){
$confirm_password_err = "Password did not match.";
}
}
// Check input errors before inserting in database
if(empty($username_err) && empty($password_err) && empty($confirm_password_err)){
// Prepare an insert statement
$sql = "INSERT INTO users (username, password) VALUES (:username, :password)";
if($stmt = $pdo->prepare($sql)){
// Bind variables to the prepared statement as parameters
$stmt->bindParam(":username", $param_username, PDO::PARAM_STR);
$stmt->bindParam(":password", $param_password, PDO::PARAM_STR);
// Set parameters
$param_username = $username;
$param_password = password_hash($password, PASSWORD_DEFAULT); // Creates a password hash
// Attempt to execute the prepared statement
if($stmt->execute()){
// Redirect to login page
header("location: login.php");
} else{
echo "Oops! Something went wrong. Please try again later.";
}
// Close statement
unset($stmt);
}
}
// Close connection
unset($pdo);
}
?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Sign Up</title>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css">
<style>
body{ font: 14px sans-serif; }
.wrapper{ width: 360px; padding: 20px; }
</style>
</head>
<body>
<div class="wrapper">
<h2>Sign Up</h2>
<p>Please fill this form to create an account.</p>
<form action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]); ?>" method="post">
<div class="form-group">
<label>Username</label>
<input type="text" name="username" class="form-control <?php echo (!empty($username_err)) ? 'is-invalid' : ''; ?>" value="<?php echo $username; ?>">
<span class="invalid-feedback"><?php echo $username_err; ?></span>
</div>
<div class="form-group">
<label>Password</label>
<input type="password" name="password" class="form-control <?php echo (!empty($password_err)) ? 'is-invalid' : ''; ?>" value="<?php echo $password; ?>">
<span class="invalid-feedback"><?php echo $password_err; ?></span>
</div>
<div class="form-group">
<label>Confirm Password</label>
<input type="password" name="confirm_password" class="form-control <?php echo (!empty($confirm_password_err)) ? 'is-invalid' : ''; ?>" value="<?php echo $confirm_password; ?>">
<span class="invalid-feedback"><?php echo $confirm_password_err; ?></span>
</div>
<div class="form-group">
<input type="submit" class="btn btn-primary" value="Submit">
<input type="reset" class="btn btn-secondary ml-2" value="Reset">
</div>
<p>Already have an account? <a href="login.php">Login here</a>.</p>
</form>
</div>
</body>
</html>
— The output of the above example (i.e., signup form) will resemble the image below:
In the example above, we've utilized PHP's built-in password_hash() function to create a hashed password from the user-entered password string (line 78). This function employs a strong one-way hashing algorithm and automatically generates and applies a random salt when hashing the password. This ensures that even if two users have the same passwords, their password hashes will differ.
During login, we will verify the provided password against the password hash stored in the database using the PHP password_verify() function, as demonstrated in the next example.
We've used the Bootstrap framework to create the form layouts quickly and elegantly. For more information about this framework, please visit the Bootstrap tutorial section.
Tip: Password salting is a technique widely used to enhance password security by randomizing password hashes. This ensures that even if two users have the same password, their password hashes will differ. Salting involves adding a random string (called a salt) to the password before hashing it.
Building the Login System
In this section, we'll create a login form where users can enter their username and password. When the user submits the form, these inputs will be verified against the credentials stored in the database. If the username and password match, the user will be authorized and granted access to the site; otherwise, the login attempt will be rejected.
Step 1: Creating the Login Form
Let's create a file named "login.php" and insert the following code into it.
Example
Procedural Object Oriented PDO
Download
<?php
// Initialize the session
session_start();
// Check if the user is already logged in, if yes then redirect him to welcome page
if(isset($_SESSION["loggedin"]) && $_SESSION["loggedin"] === true){
header("location: welcome.php");
exit;
}
// Include config file
require_once "config.php";
// Define variables and initialize with empty values
$username = $password = "";
$username_err = $password_err = $login_err = "";
// Processing form data when form is submitted
if($_SERVER["REQUEST_METHOD"] == "POST"){
// Check if username is empty
if(empty(trim($_POST["username"]))){
$username_err = "Please enter username.";
} else{
$username = trim($_POST["username"]);
}
// Check if password is empty
if(empty(trim($_POST["password"]))){
$password_err = "Please enter your password.";
} else{
$password = trim($_POST["password"]);
}
// Validate credentials
if(empty($username_err) && empty($password_err)){
// Prepare a select statement
$sql = "SELECT id, username, password FROM users WHERE username = ?";
if($stmt = mysqli_prepare($link, $sql)){
// Bind variables to the prepared statement as parameters
mysqli_stmt_bind_param($stmt, "s", $param_username);
// Set parameters
$param_username = $username;
// Attempt to execute the prepared statement
if(mysqli_stmt_execute($stmt)){
// Store result
mysqli_stmt_store_result($stmt);
// Check if username exists, if yes then verify password
if(mysqli_stmt_num_rows($stmt) == 1){
// Bind result variables
mysqli_stmt_bind_result($stmt, $id, $username, $hashed_password);
if(mysqli_stmt_fetch($stmt)){
if(password_verify($password, $hashed_password)){
// Password is correct, so start a new session
session_start();
// Store data in session variables
$_SESSION["loggedin"] = true;
$_SESSION["id"] = $id;
$_SESSION["username"] = $username;
// Redirect user to welcome page
header("location: welcome.php");
} else{
// Password is not valid, display a generic error message
$login_err = "Invalid username or password.";
}
}
} else{
// Username doesn't exist, display a generic error message
$login_err = "Invalid username or password.";
}
} else{
echo "Oops! Something went wrong. Please try again later.";
}
// Close statement
mysqli_stmt_close($stmt);
}
}
// Close connection
mysqli_close($link);
}
?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Login</title>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css">
<style>
body{ font: 14px sans-serif; }
.wrapper{ width: 360px; padding: 20px; }
</style>
</head>
<body>
<div class="wrapper">
<h2>Login</h2>
<p>Please fill in your credentials to login.</p>
<?php
if(!empty($login_err)){
echo '<div class="alert alert-danger">' . $login_err . '</div>';
}
?>
<form action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]); ?>" method="post">
<div class="form-group">
<label>Username</label>
<input type="text" name="username" class="form-control <?php echo (!empty($username_err)) ? 'is-invalid' : ''; ?>" value="<?php echo $username; ?>">
<span class="invalid-feedback"><?php echo $username_err; ?></span>
</div>
<div class="form-group">
<label>Password</label>
<input type="password" name="password" class="form-control <?php echo (!empty($password_err)) ? 'is-invalid' : ''; ?>">
<span class="invalid-feedback"><?php echo $password_err; ?></span>
</div>
<div class="form-group">
<input type="submit" class="btn btn-primary" value="Login">
</div>
<p>Don't have an account? <a href="register.php">Sign up now</a>.</p>
</form>
</div>
</body>
</html>
<?php
// Initialize the session
session_start();
// Check if the user is already logged in, if yes then redirect him to welcome page
if(isset($_SESSION["loggedin"]) && $_SESSION["loggedin"] === true){
header("location: welcome.php");
exit;
}
// Include config file
require_once "config.php";
// Define variables and initialize with empty values
$username = $password = "";
$username_err = $password_err = $login_err = "";
// Processing form data when form is submitted
if($_SERVER["REQUEST_METHOD"] == "POST"){
// Check if username is empty
if(empty(trim($_POST["username"]))){
$username_err = "Please enter username.";
} else{
$username = trim($_POST["username"]);
}
// Check if password is empty
if(empty(trim($_POST["password"]))){
$password_err = "Please enter your password.";
} else{
$password = trim($_POST["password"]);
}
// Validate credentials
if(empty($username_err) && empty($password_err)){
// Prepare a select statement
$sql = "SELECT id, username, password FROM users WHERE username = ?";
if($stmt = $mysqli->prepare($sql)){
// Bind variables to the prepared statement as parameters
$stmt->bind_param("s", $param_username);
// Set parameters
$param_username = $username;
// Attempt to execute the prepared statement
if($stmt->execute()){
// Store result
$stmt->store_result();
// Check if username exists, if yes then verify password
if($stmt->num_rows == 1){
// Bind result variables
$stmt->bind_result($id, $username, $hashed_password);
if($stmt->fetch()){
if(password_verify($password, $hashed_password)){
// Password is correct, so start a new session
session_start();
// Store data in session variables
$_SESSION["loggedin"] = true;
$_SESSION["id"] = $id;
$_SESSION["username"] = $username;
// Redirect user to welcome page
header("location: welcome.php");
} else{
// Password is not valid, display a generic error message
$login_err = "Invalid username or password.";
}
}
} else{
// Username doesn't exist, display a generic error message
$login_err = "Invalid username or password.";
}
} else{
echo "Oops! Something went wrong. Please try again later.";
}
// Close statement
$stmt->close();
}
}
// Close connection
$mysqli->close();
}
?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Login</title>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css">
<style>
body{ font: 14px sans-serif; }
.wrapper{ width: 360px; padding: 20px; }
</style>
</head>
<body>
<div class="wrapper">
<h2>Login</h2>
<p>Please fill in your credentials to login.</p>
<?php
if(!empty($login_err)){
echo '<div class="alert alert-danger">' . $login_err . '</div>';
}
?>
<form action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]); ?>" method="post">
<div class="form-group">
<label>Username</label>
<input type="text" name="username" class="form-control <?php echo (!empty($username_err)) ? 'is-invalid' : ''; ?>" value="<?php echo $username; ?>">
<span class="invalid-feedback"><?php echo $username_err; ?></span>
</div>
<div class="form-group">
<label>Password</label>
<input type="password" name="password" class="form-control <?php echo (!empty($password_err)) ? 'is-invalid' : ''; ?>">
<span class="invalid-feedback"><?php echo $password_err; ?></span>
</div>
<div class="form-group">
<input type="submit" class="btn btn-primary" value="Login">
</div>
<p>Don't have an account? <a href="register.php">Sign up now</a>.</p>
</form>
</div>
</body>
</html>
<?php
// Initialize the session
session_start();
// Check if the user is already logged in, if yes then redirect him to welcome page
if(isset($_SESSION["loggedin"]) && $_SESSION["loggedin"] === true){
header("location: welcome.php");
exit;
}
// Include config file
require_once "config.php";
// Define variables and initialize with empty values
$username = $password = "";
$username_err = $password_err = $login_err = "";
// Processing form data when form is submitted
if($_SERVER["REQUEST_METHOD"] == "POST"){
// Check if username is empty
if(empty(trim($_POST["username"]))){
$username_err = "Please enter username.";
} else{
$username = trim($_POST["username"]);
}
// Check if password is empty
if(empty(trim($_POST["password"]))){
$password_err = "Please enter your password.";
} else{
$password = trim($_POST["password"]);
}
// Validate credentials
if(empty($username_err) && empty($password_err)){
// Prepare a select statement
$sql = "SELECT id, username, password FROM users WHERE username = :username";
if($stmt = $pdo->prepare($sql)){
// Bind variables to the prepared statement as parameters
$stmt->bindParam(":username", $param_username, PDO::PARAM_STR);
// Set parameters
$param_username = trim($_POST["username"]);
// Attempt to execute the prepared statement
if($stmt->execute()){
// Check if username exists, if yes then verify password
if($stmt->rowCount() == 1){
if($row = $stmt->fetch()){
$id = $row["id"];
$username = $row["username"];
$hashed_password = $row["password"];
if(password_verify($password, $hashed_password)){
// Password is correct, so start a new session
session_start();
// Store data in session variables
$_SESSION["loggedin"] = true;
$_SESSION["id"] = $id;
$_SESSION["username"] = $username;
// Redirect user to welcome page
header("location: welcome.php");
} else{
// Password is not valid, display a generic error message
$login_err = "Invalid username or password.";
}
}
} else{
// Username doesn't exist, display a generic error message
$login_err = "Invalid username or password.";
}
} else{
echo "Oops! Something went wrong. Please try again later.";
}
// Close statement
unset($stmt);
}
}
// Close connection
unset($pdo);
}
?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Login</title>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css">
<style>
body{ font: 14px sans-serif; }
.wrapper{ width: 360px; padding: 20px; }
</style>
</head>
<body>
<div class="wrapper">
<h2>Login</h2>
<p>Please fill in your credentials to login.</p>
<?php
if(!empty($login_err)){
echo '<div class="alert alert-danger">' . $login_err . '</div>';
}
?>
<form action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]); ?>" method="post">
<div class="form-group">
<label>Username</label>
<input type="text" name="username" class="form-control <?php echo (!empty($username_err)) ? 'is-invalid' : ''; ?>" value="<?php echo $username; ?>">
<span class="invalid-feedback"><?php echo $username_err; ?></span>
</div>
<div class="form-group">
<label>Password</label>
<input type="password" name="password" class="form-control <?php echo (!empty($password_err)) ? 'is-invalid' : ''; ?>">
<span class="invalid-feedback"><?php echo $password_err; ?></span>
</div>
<div class="form-group">
<input type="submit" class="btn btn-primary" value="Login">
</div>
<p>Don't have an account? <a href="register.php">Sign up now</a>.</p>
</form>
</div>
</body>
</html>
— The output of the above example (i.e., login form) will resemble the image below:
Step 2: Creating the Welcome Page
Below is the code for our "welcome.php" file, where the user is redirected after successful login.
<?php
// Initialize the session
session_start();
// Check if the user is logged in, if not then redirect him to login page
if(!isset($_SESSION["loggedin"]) || $_SESSION["loggedin"] !== true){
header("location: login.php");
exit;
}
?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Welcome</title>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css">
<style>
body{ font: 14px sans-serif; text-align: center; }
</style>
</head>
<body>
<h1 class="my-5">Hi, <b><?php echo htmlspecialchars($_SESSION["username"]); ?></b>. Welcome to our site.</h1>
<p>
<a href="reset-password.php" class="btn btn-warning">Reset Your Password</a>
<a href="logout.php" class="btn btn-danger ml-3">Sign Out of Your Account</a>
</p>
</body>
</html>
If data originates from external sources, such as forms filled out by anonymous users, there is a risk that it may contain malicious scripts intended to launch cross-site scripting (XSS) attacks. Therefore, it's crucial to escape this data using the PHP htmlspecialchars() function before displaying it in the browser. This ensures that any HTML tags it contains become harmless.
For example, after escaping special characters, the string <script>alert("XSS")</script> becomes <script>alert("XSS")</script>, which will not be executed by the browser.
Step 3: Creating the Logout Script
Next, let's create a "logout.php" file. When the user clicks on the logout or sign out link, the script within this file will destroy the session and redirect the user back to the login page.
<?php
// Initialize the session
session_start();
// Unset all of the session variables
$_SESSION = array();
// Destroy the session.
session_destroy();
// Redirect to login page
header("location: login.php");
exit;
?>
Adding the Password Reset Feature
Finally, in this section, we will incorporate the password reset utility into our login system. With this feature, logged-in users can easily reset their own passwords for their accounts.
Let's create a file named "reset-password.php" and insert the following code into it.
Example
Procedural Object Oriented PDO
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<?php
// Initialize the session
session_start();
// Check if the user is logged in, otherwise redirect to login page
if(!isset($_SESSION["loggedin"]) || $_SESSION["loggedin"] !== true){
header("location: login.php");
exit;
}
// Include config file
require_once "config.php";
// Define variables and initialize with empty values
$new_password = $confirm_password = "";
$new_password_err = $confirm_password_err = "";
// Processing form data when form is submitted
if($_SERVER["REQUEST_METHOD"] == "POST"){
// Validate new password
if(empty(trim($_POST["new_password"]))){
$new_password_err = "Please enter the new password.";
} elseif(strlen(trim($_POST["new_password"])) < 6){
$new_password_err = "Password must have atleast 6 characters.";
} else{
$new_password = trim($_POST["new_password"]);
}
// Validate confirm password
if(empty(trim($_POST["confirm_password"]))){
$confirm_password_err = "Please confirm the password.";
} else{
$confirm_password = trim($_POST["confirm_password"]);
if(empty($new_password_err) && ($new_password != $confirm_password)){
$confirm_password_err = "Password did not match.";
}
}
// Check input errors before updating the database
if(empty($new_password_err) && empty($confirm_password_err)){
// Prepare an update statement
$sql = "UPDATE users SET password = ? WHERE id = ?";
if($stmt = mysqli_prepare($link, $sql)){
// Bind variables to the prepared statement as parameters
mysqli_stmt_bind_param($stmt, "si", $param_password, $param_id);
// Set parameters
$param_password = password_hash($new_password, PASSWORD_DEFAULT);
$param_id = $_SESSION["id"];
// Attempt to execute the prepared statement
if(mysqli_stmt_execute($stmt)){
// Password updated successfully. Destroy the session, and redirect to login page
session_destroy();
header("location: login.php");
exit();
} else{
echo "Oops! Something went wrong. Please try again later.";
}
// Close statement
mysqli_stmt_close($stmt);
}
}
// Close connection
mysqli_close($link);
}
?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Reset Password</title>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css">
<style>
body{ font: 14px sans-serif; }
.wrapper{ width: 360px; padding: 20px; }
</style>
</head>
<body>
<div class="wrapper">
<h2>Reset Password</h2>
<p>Please fill out this form to reset your password.</p>
<form action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]); ?>" method="post">
<div class="form-group">
<label>New Password</label>
<input type="password" name="new_password" class="form-control <?php echo (!empty($new_password_err)) ? 'is-invalid' : ''; ?>" value="<?php echo $new_password; ?>">
<span class="invalid-feedback"><?php echo $new_password_err; ?></span>
</div>
<div class="form-group">
<label>Confirm Password</label>
<input type="password" name="confirm_password" class="form-control <?php echo (!empty($confirm_password_err)) ? 'is-invalid' : ''; ?>">
<span class="invalid-feedback"><?php echo $confirm_password_err; ?></span>
</div>
<div class="form-group">
<input type="submit" class="btn btn-primary" value="Submit">
<a class="btn btn-link ml-2" href="welcome.php">Cancel</a>
</div>
</form>
</div>
</body>
</html>
<?php
// Initialize the session
session_start();
// Check if the user is logged in, otherwise redirect to login page
if(!isset($_SESSION["loggedin"]) || $_SESSION["loggedin"] !== true){
header("location: login.php");
exit;
}
// Include config file
require_once "config.php";
// Define variables and initialize with empty values
$new_password = $confirm_password = "";
$new_password_err = $confirm_password_err = "";
// Processing form data when form is submitted
if($_SERVER["REQUEST_METHOD"] == "POST"){
// Validate new password
if(empty(trim($_POST["new_password"]))){
$new_password_err = "Please enter the new password.";
} elseif(strlen(trim($_POST["new_password"])) < 6){
$new_password_err = "Password must have atleast 6 characters.";
} else{
$new_password = trim($_POST["new_password"]);
}
// Validate confirm password
if(empty(trim($_POST["confirm_password"]))){
$confirm_password_err = "Please confirm the password.";
} else{
$confirm_password = trim($_POST["confirm_password"]);
if(empty($new_password_err) && ($new_password != $confirm_password)){
$confirm_password_err = "Password did not match.";
}
}
// Check input errors before updating the database
if(empty($new_password_err) && empty($confirm_password_err)){
// Prepare an update statement
$sql = "UPDATE users SET password = ? WHERE id = ?";
if($stmt = $mysqli->prepare($sql)){
// Bind variables to the prepared statement as parameters
$stmt->bind_param("si", $param_password, $param_id);
// Set parameters
$param_password = password_hash($new_password, PASSWORD_DEFAULT);
$param_id = $_SESSION["id"];
// Attempt to execute the prepared statement
if($stmt->execute()){
// Password updated successfully. Destroy the session, and redirect to login page
session_destroy();
header("location: login.php");
exit();
} else{
echo "Oops! Something went wrong. Please try again later.";
}
// Close statement
$stmt->close();
}
}
// Close connection
$mysqli->close();
}
?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Reset Password</title>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css">
<style>
body{ font: 14px sans-serif; }
.wrapper{ width: 360px; padding: 20px; }
</style>
</head>
<body>
<div class="wrapper">
<h2>Reset Password</h2>
<p>Please fill out this form to reset your password.</p>
<form action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]); ?>" method="post">
<div class="form-group">
<label>New Password</label>
<input type="password" name="new_password" class="form-control <?php echo (!empty($new_password_err)) ? 'is-invalid' : ''; ?>" value="<?php echo $new_password; ?>">
<span class="invalid-feedback"><?php echo $new_password_err; ?></span>
</div>
<div class="form-group">
<label>Confirm Password</label>
<input type="password" name="confirm_password" class="form-control <?php echo (!empty($confirm_password_err)) ? 'is-invalid' : ''; ?>">
<span class="invalid-feedback"><?php echo $confirm_password_err; ?></span>
</div>
<div class="form-group">
<input type="submit" class="btn btn-primary" value="Submit">
<a class="btn btn-link ml-2" href="welcome.php">Cancel</a>
</div>
</form>
</div>
</body>
</html>
<?php
// Initialize the session
session_start();
// Check if the user is logged in, otherwise redirect to login page
if(!isset($_SESSION["loggedin"]) || $_SESSION["loggedin"] !== true){
header("location: login.php");
exit;
}
// Include config file
require_once "config.php";
// Define variables and initialize with empty values
$new_password = $confirm_password = "";
$new_password_err = $confirm_password_err = "";
// Processing form data when form is submitted
if($_SERVER["REQUEST_METHOD"] == "POST"){
// Validate new password
if(empty(trim($_POST["new_password"]))){
$new_password_err = "Please enter the new password.";
} elseif(strlen(trim($_POST["new_password"])) < 6){
$new_password_err = "Password must have atleast 6 characters.";
} else{
$new_password = trim($_POST["new_password"]);
}
// Validate confirm password
if(empty(trim($_POST["confirm_password"]))){
$confirm_password_err = "Please confirm the password.";
} else{
$confirm_password = trim($_POST["confirm_password"]);
if(empty($new_password_err) && ($new_password != $confirm_password)){
$confirm_password_err = "Password did not match.";
}
}
// Check input errors before updating the database
if(empty($new_password_err) && empty($confirm_password_err)){
// Prepare an update statement
$sql = "UPDATE users SET password = :password WHERE id = :id";
if($stmt = $pdo->prepare($sql)){
// Bind variables to the prepared statement as parameters
$stmt->bindParam(":password", $param_password, PDO::PARAM_STR);
$stmt->bindParam(":id", $param_id, PDO::PARAM_INT);
// Set parameters
$param_password = password_hash($new_password, PASSWORD_DEFAULT);
$param_id = $_SESSION["id"];
// Attempt to execute the prepared statement
if($stmt->execute()){
// Password updated successfully. Destroy the session, and redirect to login page
session_destroy();
header("location: login.php");
exit();
} else{
echo "Oops! Something went wrong. Please try again later.";
}
// Close statement
unset($stmt);
}
}
// Close connection
unset($pdo);
}
?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Reset Password</title>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css">
<style>
body{ font: 14px sans-serif; }
.wrapper{ width: 360px; padding: 20px; }
</style>
</head>
<body>
<div class="wrapper">
<h2>Reset Password</h2>
<p>Please fill out this form to reset your password.</p>
<form action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]); ?>" method="post">
<div class="form-group">
<label>New Password</label>
<input type="password" name="new_password" class="form-control <?php echo (!empty($new_password_err)) ? 'is-invalid' : ''; ?>" value="<?php echo $new_password; ?>">
<span class="invalid-feedback"><?php echo $new_password_err; ?></span>
</div>
<div class="form-group">
<label>Confirm Password</label>
<input type="password" name="confirm_password" class="form-control <?php echo (!empty($confirm_password_err)) ? 'is-invalid' : ''; ?>">
<span class="invalid-feedback"><?php echo $confirm_password_err; ?></span>
</div>
<div class="form-group">
<input type="submit" class="btn btn-primary" value="Submit">
<a class="btn btn-link ml-2" href="welcome.php">Cancel</a>
</div>
</form>
</div>
</body>
</html>
