$fb = new Facebook\Facebook([
  'app_id' => 'FB_APP_ID',
  'app_secret' => 'FB_APP_SECRET',
  'default_graph_version' => 'v19.0',
]);

$helper = $fb->getRedirectLoginHelper();
$permissions = ['email'];
$loginUrl = $helper->getLoginUrl(
    'https://rangkaimediapublishing-digitallibrary.my.id/oauth/facebook_callback.php',
    $permissions
);

header("Location: $loginUrl");
exit;