function sync_order_callback()
{
    global $wpdb;
    // this is how you get access to the database
    include_once "class-woo-fortnox-controller.php";
    check_ajax_referer('fortnox_woocommerce', 'security');
    $controller = new WC_Fortnox_Controller();
    $message = $controller->send_contact_to_fortnox($_POST['order_id']);
    echo json_encode($message);
    die;
    // this is required to return a proper result
}
 /**
  * Sends contact of given order to Fortnox API
  *
  * @access public
  * @param int $orderId
  */
 public function synchronize_order_on_complete($orderId)
 {
     include_once "class-woo-fortnox-controller.php";
     $options = get_option('woocommerce_fortnox_general_settings');
     if (!isset($options['activate-automatic-orders'])) {
         return;
     }
     $controller = new WC_Fortnox_Controller();
     $controller->send_contact_to_fortnox($orderId);
 }