What are the potential pitfalls of relying on Facebook Graph API for user authentication in PHP?

Potential pitfalls of relying on Facebook Graph API for user authentication in PHP include: 1. Dependency on a third-party service: If Facebook Graph API experiences downtime or changes its authentication process, it could disrupt your application's functionality. 2. Limited control over user data: When using Facebook Graph API for authentication, you are relying on Facebook to handle user data securely, which may raise privacy concerns. 3. Complex integration: Implementing Facebook Graph API authentication in PHP requires understanding OAuth protocols and proper error handling to ensure a smooth user experience. To mitigate these risks, consider implementing a fallback authentication method or providing users with alternative login options to reduce dependency on Facebook Graph API.

// Fallback authentication method using a local database
if (isset($_SESSION['user_id'])) {
    // User is already authenticated, retrieve user data from local database
    $user_id = $_SESSION['user_id'];
    $user = getUserDataFromDatabase($user_id);
} else {
    // User is not authenticated, prompt for login using Facebook Graph API
    header('Location: https://www.facebook.com/v12.0/dialog/oauth?client_id=YOUR_APP_ID&redirect_uri=YOUR_REDIRECT_URI&scope=email');
}

function getUserDataFromDatabase($user_id) {
    // Implement logic to retrieve user data from a local database
    return $user_data;
}