Untitled

<?php
    session_start();

    if(isset($_COOKIE['username'])) {
        header('Location: account.php');
    }
?>
<!DOCTYPE html>
<html>
<head>
    <title>Sample</title>
</head>
<body>
<?php if(isset($_SESSION['login_error'])): ?>
    <div class="error_message">Incorrect username and password combination</div>
<?php endif; ?>
<form action="login.php" method="post">
    <input type="text" name="username" placeholder="Username" autocomplete="off"><br>
    <input type="password" name="password" placeholder="Password"><br>
    <input type="submit" value="Log in">
</form>

<?php
session_start();

$db = new PDO('mysql:host=127.0.0.1;dbname=sample;charset=utf8', 'root', '');

if(isset($_POST['username'], $_POST['password'])) {
    if(!empty($_POST['username']) && !empty($_POST['password'])) {
        $query = $db->prepare("SELECT username, lastname FROM users WHERE username=:username AND password=:password");
        $query->execute([
            'username' => $_POST['username'],
            'password' => $_POST['password']
        ]);

        $row = $query->fetchAll(PDO::FETCH_OBJ);

        if(count($row)) {
            $_SESSION['username'] = $_POST['username'];
            setcookie('username', $_POST['username'], time()+3600);
            header('Location: account.php');
        } else {
            $_SESSION['login_error'] = 'Incorrect username and password combination';
            header('Location: index.php');
        }
    } else {
        header('Location: index.php');
    }
}

<?php
    session_start();

    if(!isset($_COOKIE['username'])) {
        header('Location: index.php');
    }

    $db = new PDO('mysql:host=127.0.0.1;dbname=sample;charset=utf8', 'root', '');
    $query = $db->prepare("SELECT firstname, lastname FROM users WHERE username=:username");

    $query->execute(['username' => $_SESSION['username']]);

    $row = $query->fetchAll(PDO::FETCH_OBJ);
?>
<!DOCTYPE html>
<html>
<head>
    <title>Account</title>
</head>
<body>
    <?php if(isset($_SESSION['username'])): ?>
        <div>Hello, <?php echo $row->firstname; ?></div>
    <?php endif; ?>

    <a href="logout.php">Logout</a>
</body>
</html>