require_once 'vendor/autoload.php';

$fb = new \Facebook\Facebook([
  'app_id' => 'YOUR_FACEBOOK_APP_ID',
  'app_secret' => 'YOUR_FACEBOOK_APP_SECRET',
  'default_graph_version' => 'v11.0',
]);

$helper = $fb->getRedirectLoginHelper();
$permissions = ['email']; // Optional permissions
$loginUrl = $helper->getLoginUrl('https://yourdomain.com/login/facebook_callback.php', $permissions);

header('Location: ' . htmlspecialchars($loginUrl));