public function setUpOnce()
{
if (!ShoppingCart_Controller::has_extension('ShoppingCartAjax')) {
ShoppingCart_Controller::add_extension('ShoppingCartAjax');
}
if (!VariationForm::has_extension('ShoppingCartAjax')) {
VariationForm::add_extension('ShoppingCartAjax');
}
if (!Controller::has_extension('AjaxControllerExtension')) {
Controller::add_extension('AjaxControllerExtension');
}
parent::setUpOnce();
}