What are the potential pitfalls of using sessions in PHP applications, especially when integrating with external platforms like Facebook?

Potential pitfalls of using sessions in PHP applications, especially when integrating with external platforms like Facebook, include session hijacking, session fixation, and session data leakage. To mitigate these risks, it is recommended to use secure session handling techniques such as regenerating session IDs after successful authentication, using HTTPS to encrypt session data, and validating session data before processing.

// Start a secure session
session_start([
    'cookie_secure' => true,
    'cookie_httponly' => true
]);

// Regenerate session ID after successful authentication
if ($authenticated) {
    session_regenerate_id(true);
}

// Validate session data before processing
if (isset($_SESSION['user_id'])) {
    // Process session data
} else {
    // Redirect to login page
}