In: Computer Science
Using PHP
Provide and the ability for the user to determine their userid and to change their password if they forget either.
Also, provide the ability for the user to change the password whenever they chose. If they are changing their password (when they know the password), they must be required to enter the old password, and then the new password (twice).
Anytime the password is changed it must verify the correct format of the password as previously mentioned in other assignments.
Make sure that your program works properly.
1.register.php
<?php include('functions.php') ?>
<!DOCTYPE html>
<html>
<head>
        <title>Registration system PHP and MySQL</title>
        <link rel="stylesheet" type="text/css" href="style.css">
</head>
<body>
        <div class="header">
                <h2>Register</h2>
        </div>
        
        <form method="post" action="register.php">
                <?php echo display_error(); ?>
                <div class="input-group">
                        <label>Username</label>
                        <input type="text" name="username" value="<?php echo $username; ?>">
                </div>
                <div class="input-group">
                        <label>Email</label>
                        <input type="email" name="email" value="<?php echo $email; ?>">
                </div>
                <div class="input-group">
                        <label>Password</label>
                        <input type="password" name="password_1">
                </div>
                <div class="input-group">
                        <label>Confirm password</label>
                        <input type="password" name="password_2">
                </div>
                <div class="input-group">
                        <button type="submit" class="btn" name="register_btn">Register</button>
                </div>
                <p>
                        Already a member? <a href="login.php">Sign in</a>
                </p>
        </form>
</body>
</html>
2.login.php
<?php include('functions.php') ?>
<!DOCTYPE html>
<html>
<head>
        <title>Registration system PHP and MySQL</title>
        <link rel="stylesheet" type="text/css" href="style.css">
</head>
<body>
        <div class="header">
                <h2>Login</h2>
        </div>
        
        <form method="post" action="login.php">
                <?php echo display_error(); ?>
                <div class="input-group">
                        <label>Username</label>
                        <input type="text" name="username" >
                </div>
                <div class="input-group">
                        <label>Password</label>
                        <input type="password" name="password">
                </div>
                <div class="input-group">
                        <button type="submit" class="btn" name="login_btn">Login</button>
                </div>
                <p>
                        Not yet a member? <a href="register.php">Sign up</a>
                </p>
        </form>
</body>
</html>
3.style.css
* {
        margin: 0px;
        padding: 0px;
}
body {
        font-size: 120%;
        background: #F8F8FF;
}
.header {
        width: 40%;
        margin: 50px auto 0px;
        color: white;
        background: #5F9EA0;
        text-align: center;
        border: 1px solid #B0C4DE;
        border-bottom: none;
        border-radius: 10px 10px 0px 0px;
        padding: 20px;
}
form, .content {
        width: 40%;
        margin: 0px auto;
        padding: 20px;
        border: 1px solid #B0C4DE;
        background: white;
        border-radius: 0px 0px 10px 10px;
}
.input-group {
        margin: 10px 0px 10px 0px;
}
.input-group label {
        display: block;
        text-align: left;
        margin: 3px;
}
.input-group input {
        height: 30px;
        width: 93%;
        padding: 5px 10px;
        font-size: 16px;
        border-radius: 5px;
        border: 1px solid gray;
}
#user_type {
        height: 40px;
        width: 98%;
        padding: 5px 10px;
        background: white;
        font-size: 16px;
        border-radius: 5px;
        border: 1px solid gray;
}
.btn {
        padding: 10px;
        font-size: 15px;
        color: white;
        background: #5F9EA0;
        border: none;
        border-radius: 5px;
}
.error {
        width: 92%; 
        margin: 0px auto; 
        padding: 10px; 
        border: 1px solid #a94442; 
        color: #a94442; 
        background: #f2dede; 
        border-radius: 5px; 
        text-align: left;
}
.success {
        color: #3c763d; 
        background: #dff0d8; 
        border: 1px solid #3c763d;
        margin-bottom: 20px;
}
.profile_info img {
        display: inline-block; 
        width: 50px; 
        height: 50px; 
        margin: 5px;
        float: left;
}
.profile_info div {
        display: inline-block; 
        margin: 5px;
}
.profile_info:after {
        content: "";
        display: block;
        clear: both;
}
4.home.php
<?php 
        include('../functions.php');
        if (!isAdmin()) {
                $_SESSION['msg'] = "You must log in first";
                header('location: ../login.php');
        }
?>
<!DOCTYPE html>
<html>
<head>
        <title>Home</title>
        <link rel="stylesheet" type="text/css" href="../style.css">
        <style>
        .header {
                background: #003366;
        }
        button[name=register_btn] {
                background: #003366;
        }
        </style>
</head>
<body>
        <div class="header">
                <h2>Admin - Home Page</h2>
        </div>
        <div class="content">
                <!-- notification message -->
                <?php if (isset($_SESSION['success'])) : ?>
                        <div class="error success" >
                                <h3>
                                        <?php 
                                                echo $_SESSION['success']; 
                                                unset($_SESSION['success']);
                                        ?>
                                </h3>
                        </div>
                <?php endif ?>
                <!-- logged in user information -->
                <div class="profile_info">
                        <img src="../images/admin_profile.png"  >
                        <div>
                                <?php  if (isset($_SESSION['user'])) : ?>
                                        <strong><?php echo $_SESSION['user']['username']; ?></strong>
                                        <small>
                                                <i  style="color: #888;">(<?php echo ucfirst($_SESSION['user']['user_type']); ?>)</i> 
                                                <br>
                                                <a href="home.php?logout='1'" style="color: red;">logout</a>
                                                  <a href="create_user.php"> + add user</a>
                                        </small>
                                <?php endif ?>
                        </div>
                </div>
        </div>
                
</body>
</html>
5.functions.php
<?php 
        session_start();
        // connect to database
        $db = mysqli_connect('localhost', 'root', '', 'multi_login');
        // variable declaration
        $username = "";
        $email    = "";
        $errors   = array(); 
        // call the register() function if register_btn is clicked
        if (isset($_POST['register_btn'])) {
                register();
        }
        // call the login() function if register_btn is clicked
        if (isset($_POST['login_btn'])) {
                login();
        }
        if (isset($_GET['logout'])) {
                session_destroy();
                unset($_SESSION['user']);
                header("location: ../login.php");
        }
        // REGISTER USER
        function register(){
                global $db, $errors;
                // receive all input values from the form
                $username    =  e($_POST['username']);
                $email       =  e($_POST['email']);
                $password_1  =  e($_POST['password_1']);
                $password_2  =  e($_POST['password_2']);
                // form validation: ensure that the form is correctly filled
                if (empty($username)) { 
                        array_push($errors, "Username is required"); 
                }
                if (empty($email)) { 
                        array_push($errors, "Email is required"); 
                }
                if (empty($password_1)) { 
                        array_push($errors, "Password is required"); 
                }
                if ($password_1 != $password_2) {
                        array_push($errors, "The two passwords do not match");
                }
                // register user if there are no errors in the form
                if (count($errors) == 0) {
                        $password = md5($password_1);//encrypt the password before saving in the database
                        if (isset($_POST['user_type'])) {
                                $user_type = e($_POST['user_type']);
                                $query = "INSERT INTO users (username, email, user_type, password) 
                                                  VALUES('$username', '$email', '$user_type', '$password')";
                                mysqli_query($db, $query);
                                $_SESSION['success']  = "New user successfully created!!";
                                header('location: home.php');
                        }else{
                                $query = "INSERT INTO users (username, email, user_type, password) 
                                                  VALUES('$username', '$email', 'user', '$password')";
                                mysqli_query($db, $query);
                                // get id of the created user
                                $logged_in_user_id = mysqli_insert_id($db);
                                $_SESSION['user'] = getUserById($logged_in_user_id); // put logged in user in session
                                $_SESSION['success']  = "You are now logged in";
                                header('location: index.php');                          
                        }
                }
        }
        // return user array from their id
        function getUserById($id){
                global $db;
                $query = "SELECT * FROM users WHERE id=" . $id;
                $result = mysqli_query($db, $query);
                $user = mysqli_fetch_assoc($result);
                return $user;
        }
        // LOGIN USER
        function login(){
                global $db, $username, $errors;
                // grap form values
                $username = e($_POST['username']);
                $password = e($_POST['password']);
                // make sure form is filled properly
                if (empty($username)) {
                        array_push($errors, "Username is required");
                }
                if (empty($password)) {
                        array_push($errors, "Password is required");
                }
                // attempt login if no errors on form
                if (count($errors) == 0) {
                        $password = md5($password);
                        $query = "SELECT * FROM users WHERE username='$username' AND password='$password' LIMIT 1";
                        $results = mysqli_query($db, $query);
                        if (mysqli_num_rows($results) == 1) { // user found
                                // check if user is admin or user
                                $logged_in_user = mysqli_fetch_assoc($results);
                                if ($logged_in_user['user_type'] == 'admin') {
                                        $_SESSION['user'] = $logged_in_user;
                                        $_SESSION['success']  = "You are now logged in";
                                        header('location: admin/home.php');               
                                }else{
                                        $_SESSION['user'] = $logged_in_user;
                                        $_SESSION['success']  = "You are now logged in";
                                        header('location: index.php');
                                }
                        }else {
                                array_push($errors, "Wrong username/password combination");
                        }
                }
        }
        function isLoggedIn()
        {
                if (isset($_SESSION['user'])) {
                        return true;
                }else{
                        return false;
                }
        }
        function isAdmin()
        {
                if (isset($_SESSION['user']) && $_SESSION['user']['user_type'] == 'admin' ) {
                        return true;
                }else{
                        return false;
                }
        }
        // escape string
        function e($val){
                global $db;
                return mysqli_real_escape_string($db, trim($val));
        }
        function display_error() {
                global $errors;
                if (count($errors) > 0){
                        echo '<div class="error">';
                                foreach ($errors as $error){
                                        echo $error .'<br>';
                                }
                        echo '</div>';
                }
        }
?>
6.index.php
<?php 
        include('functions.php');
        if (!isLoggedIn()) {
                $_SESSION['msg'] = "You must log in first";
                header('location: login.php');
        }
?>
<!DOCTYPE html>
<html>
<head>
        <title>Home</title>
        <link rel="stylesheet" type="text/css" href="style.css">
</head>
<body>
        <div class="header">
                <h2>Home Page</h2>
        </div>
        <div class="content">
                <!-- notification message -->
                <?php if (isset($_SESSION['success'])) : ?>
                        <div class="error success" >
                                <h3>
                                        <?php 
                                                echo $_SESSION['success']; 
                                                unset($_SESSION['success']);
                                        ?>
                                </h3>
                        </div>
                <?php endif ?>
                <!-- logged in user information -->
                <div class="profile_info">
                        <img src="images/user_profile.png"  >
                        <div>
                                <?php  if (isset($_SESSION['user'])) : ?>
                                        <strong><?php echo $_SESSION['user']['username']; ?></strong>
                                        <small>
                                                <i  style="color: #888;">(<?php echo ucfirst($_SESSION['user']['user_type']); ?>)</i> 
                                                <br>
                                                <a href="index.php?logout='1'" style="color: red;">logout</a>
                                        </small>
                                <?php endif ?>
                        </div>
                </div>
        </div>
</body>
</html>
7.create_user.php
<?php include('../functions.php') ?>
<!DOCTYPE html>
<html>
<head>
        <title>Registration system PHP and MySQL - Create user</title>
        <link rel="stylesheet" type="text/css" href="../style.css">
        <style>
                .header {
                        background: #003366;
                }
                button[name=register_btn] {
                        background: #003366;
                }
        </style>
</head>
<body>
        <div class="header">
                <h2>Admin - create user</h2>
        </div>
        
        <form method="post" action="create_user.php">
                <?php echo display_error(); ?>
                <div class="input-group">
                        <label>Username</label>
                        <input type="text" name="username" value="<?php echo $username; ?>">
                </div>
                <div class="input-group">
                        <label>Email</label>
                        <input type="email" name="email" value="<?php echo $email; ?>">
                </div>
                <div class="input-group">
                        <label>User type</label>
                        <select name="user_type" id="user_type" >
                                <option value=""></option>
                                <option value="admin">Admin</option>
                                <option value="user">User</option>
                        </select>
                </div>
                <div class="input-group">
                        <label>Password</label>
                        <input type="password" name="password_1">
                </div>
                <div class="input-group">
                        <label>Confirm password</label>
                        <input type="password" name="password_2">
                </div>
                <div class="input-group">
                        <button type="submit" class="btn" name="register_btn"> + Create user</button>
                </div>
        </form>
</body>
</html>
Summary:
The following code contains a whole structure like Register(SignUp), Login Page, functions(like login, logout, admin, etc). There is also a database function where it stores the user info.
Note: Put all the codes in the same folder in order to run with errors.
Note: If you find any error or if i had missed something then please let me know through comments.