// stores the reference to the XMLHttpRequest object
var xmlHttp = createXmlHttpRequestObject();
// retrieves the XMLHttpRequest object
function createXmlHttpRequestObject() {
	// will store the reference to the XMLHttpRequest object
	var xmlHttp;
	// if running Internet Explorer
	if (window.ActiveXObject) {
		try {
			xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
		} catch (e) {
			xmlHttp = false;
		}
	}
	// if running Mozilla or other browsers
	else {
		try {
			xmlHttp = new XMLHttpRequest();
		} catch (e) {
			xmlHttp = false;
		}
	}
	// return the created object or display an error message
	if (!xmlHttp)
		alert("Error creating the XMLHttpRequest object.");
	else
		return xmlHttp;
}

// make asynchronous HTTP request using the XMLHttpRequest object
function add2cart(itemid) {	
	// proceed only if the xmlHttp object isn't busy
	if (xmlHttp.readyState == 4 || xmlHttp.readyState == 0) {
		var basketsrc = document.getElementById("imgbasket"+itemid).src;
		if (basketsrc.indexOf("chek-green.gif") == -1 )
			{
				// execute the quickstart.php page from the server
				var imageid = "quantity"+itemid;
				var quantity = document.getElementById("quantity"+itemid).value;
				var qry = "add2cart.php?itemid=" + itemid + "&quantity="+quantity;
				xmlHttp.open("GET", qry, true);
				// define the method to handle server responses
				xmlHttp.onreadystatechange = handleServerResponse;
				// make the server request
				xmlHttp.send(null);
			}
	}
//	else
//		// if the connection is busy, try again after one second
//		setTimeout("add2cart(itemid)", 1000);
}
// executed automatically when a message is received from the server
function handleServerResponse() {	
	// move forward only if the transaction has completed
	if (xmlHttp.readyState == 4) {
		// status of 200 indicates the transaction completed successfully		
		if (xmlHttp.status == 200) {			
			// extract the XML retrieved from the server
			xmlResponse = xmlHttp.responseXML;
			// obtain the document element (the root element) of the XML
			// structure
			xmlDocumentElement = xmlResponse.documentElement;
			// get the text message, which is in the first child of
			// the the document element
			itemid = xmlDocumentElement.firstChild.data;			
			if (itemid != "error")
			{				
				document.getElementById("imgbasket"+itemid).src = "../i/chek-green.gif"				
				document.getElementById("quantity"+itemid).disabled = true;		
			    if (window.opener)
			    {
			    	window.opener.location.reload();
			    }
				
			}			
			
			// restart sequence
			// setTimeout("add2cart(itemid)", 1000);
		}
		// a HTTP status different than 200 signals an error
		else {
			alert("There was a problem accessing the server: "
					+ xmlHttp.statusText);
		}
	}
}