var xmlHttp=null;
function GetXmlHttpObject()
{
  var xmlHttp=null;
  try
    {
    // Firefox, Opera 8.0+, Safari
    xmlHttp=new XMLHttpRequest();
    }
  catch (e)
    {
    // Internet Explorer
    try
      {
      xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
      }
    catch (e)
      {
      xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
      }
    }
  return xmlHttp;
}

function IsNumeric(sText)
{
   var ValidChars = "0123456789.";
   var IsNumber=true;
   var Char;


   for (i = 0; i < sText.length && IsNumber == true; i++)
      {
      Char = sText.charAt(i);
      if (ValidChars.indexOf(Char) == -1)
         {
         IsNumber = false;
         }
      }
   return IsNumber;
}

function getURL (url,fn)
{
	//alert(url);
	xmlHttp=GetXmlHttpObject();
	if (xmlHttp==null)
    {
      alert ("Your browser does not support AJAX!");
      return;
    }
    xmlHttp.onreadystatechange=fn;
    xmlHttp.open("GET",url,true);
    xmlHttp.send(null);
}

function displayResults()
{
    if (xmlHttp.readyState==4)
    {
	var xmlDoc=xmlHttp.responseXML.documentElement;
	var node = xmlDoc.getElementsByTagName("result");
	document.getElementById("HiddenCarbs").innerHTML = node[0].getAttribute("HiddenCarbs");
    }
}

function calc(form)
{
	if ((form.Fats.value == '') || (! IsNumeric(form.Fats.value)))
	{
		document.getElementById("msg").innerHTML = "<b>Invaid Fats</b>";
		return ;
	}
	if ((form.Carbs.value == '') || (! IsNumeric(form.Carbs.value)))
	{
		document.getElementById("msg").innerHTML = "<b>Invaid Carbs</b>";
		return ;
	}
	if ((form.Protein.value == '') || (! IsNumeric(form.Protein.value)))
	{
		document.getElementById("msg").innerHTML = "<b>Invaid Protein</b>";
		return ;
	}
	if ((form.Calories.value == '') || (! IsNumeric(form.Calories.value)))
	{
		document.getElementById("msg").innerHTML = "<b>Invaid Calories</b>";
		return ;
	}
	var url = "hidden.php?";
	url = url + "txtFats=" + document.getElementById("Fats").value;
        url = url + "&txtCarbs=" + document.getElementById("Carbs").value;
        url = url + "&txtProtein=" + document.getElementById("Protein").value;
        url = url + "&txtCalories=" + document.getElementById("Calories").value;
	document.getElementById("msg").innerHTML = '';
	getURL(url , displayResults);
}