How can one ensure that unauthorized access is prevented when using PHP for login authentication?

To prevent unauthorized access when using PHP for login authentication, it is essential to properly sanitize user input, use secure password hashing techniques, and implement session management to track authenticated users. Additionally, implementing measures such as rate limiting, CAPTCHA verification, and two-factor authentication can further enhance security. 

// Sample PHP code snippet for login authentication with prevention of unauthorized access

// Sanitize user input
$username = filter_var($_POST['username'], FILTER_SANITIZE_STRING);
$password = filter_var($_POST['password'], FILTER_SANITIZE_STRING);

// Secure password hashing
$hashed_password = password_hash($password, PASSWORD_DEFAULT);

// Verify user credentials
if ($username === "example_user" && password_verify($password, $hashed_password)) {
    // Start session and set user as authenticated
    session_start();
    $_SESSION['authenticated'] = true;
    // Redirect user to authenticated page
    header("Location: authenticated_page.php");
    exit();
} else {
    // Invalid credentials, redirect back to login page
    header("Location: login.php?error=invalid_credentials");
    exit();
}

Keywords

PHP login authentication password hashing session management CSRF protection

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