What are best practices for handling user authentication in PHP scripts to avoid security vulnerabilities?

To avoid security vulnerabilities when handling user authentication in PHP scripts, it is important to use secure password hashing algorithms, such as bcrypt, to store user passwords. Additionally, always use prepared statements or parameterized queries to prevent SQL injection attacks. Implementing session management and using HTTPS to encrypt data transmission are also crucial for securing user authentication. 

// Sample PHP code snippet for secure user authentication
// Using bcrypt for password hashing and prepared statements to prevent SQL injection

// Hashing the user's password with bcrypt
$password = $_POST['password'];
$hashed_password = password_hash($password, PASSWORD_BCRYPT);

// Using prepared statements to query the database for user authentication
$stmt = $pdo->prepare("SELECT * FROM users WHERE username = :username");
$stmt->bindParam(':username', $_POST['username']);
$stmt->execute();
$user = $stmt->fetch();

if($user && password_verify($_POST['password'], $user['password'])){
    // User authentication successful
    // Start session and redirect to secure page
    session_start();
    $_SESSION['user_id'] = $user['id'];
    header('Location: secure_page.php');
} else {
    // User authentication failed
    // Redirect back to login page with error message
    header('Location: login.php?error=1');
}

Keywords

SQL injection password hashing session management CSRF protection secure cookies

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