What are the best practices for handling user input and authentication in PHP scripts like the one provided in the forum thread?

The best practices for handling user input and authentication in PHP scripts include validating and sanitizing user input to prevent SQL injection and cross-site scripting attacks, using prepared statements for database queries to prevent SQL injection, hashing passwords before storing them in the database, and implementing secure authentication mechanisms like session management and CSRF protection. 

// Validate and sanitize user input
$username = filter_input(INPUT_POST, 'username', FILTER_SANITIZE_STRING);
$password = filter_input(INPUT_POST, 'password', FILTER_SANITIZE_STRING);

// Hash the password before storing it in the database
$hashed_password = password_hash($password, PASSWORD_DEFAULT);

// Use prepared statements for database queries to prevent SQL injection
$stmt = $pdo->prepare("SELECT * FROM users WHERE username = :username");
$stmt->bindParam(':username', $username);
$stmt->execute();
$user = $stmt->fetch();

// Verify password using password_verify function
if ($user && password_verify($password, $user['password'])) {
    // Authentication successful
    $_SESSION['user_id'] = $user['id'];
    header('Location: dashboard.php');
    exit();
} else {
    // Authentication failed
    echo 'Invalid username or password';
}

Keywords

input validation user authentication PHP security password hashing SQL injection

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