Adding multiple products to cart

[Eduvi]

First of all, sorry for my English.

I found how to add multiple products into cart using AJAX, with registered users it works properly but I have some problems with "guest" users.

I created this function. I call it for every product selected in the view, the id's and quantities I pass to this method are correct.

function add_product_to_cart(id, qtt){
	var token = prestashop.static_token;
	var actionURL = prestashop.urls.pages.cart;
	var query= 'controller=cart&add=1&ajax=true&token='+token+'&id_product='+ id +'&qty='+qtt+'&ajaxIdentifier='+ajaxIdentifier;
	jQuery.ajax({
  		type: 'POST',
  		headers: { "cache-control": "no-cache" },
  		async: true,
  		cache: false,
  		data: query,
  		success:function(result){
    		prestashop.emit('updateCart', {
      			reason: result
    		});
  		},
  		fail:function(resp){
    		prestashop.emit('handleError', { eventType: 'addProductToCart', resp: resp });
  		}
	});
}

When I (as guest) add multiple products into the cart this way, it creates a cart for every different product I'm trying to add, but only happens the first time after I clean the cookies. After the first addition "guest" users can add the products as normal and uses the last cart created.

I need to create just one cart and add all the selected products with its quantities to this cart. How can avoid this problem?