function isNumberKey(evt)
{
   var charCode = (evt.which) ? evt.which : event.keyCode
   if (charCode > 31 && (charCode < 48 || charCode > 57))
      return false;

   return true;

}

function updateCategory() {
	var selectbox = document.getElementById('selectCategory');
	var catid = selectbox.options[selectbox.selectedIndex].value;
	httpobj = get_ajaxobject();
	httpobj.onreadystatechange = function() { changeType(httpobj); };
	httpobj.open('GET', '/category.inc.php?category='+catid ,true);
	httpobj.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
	httpobj.send(null);
}

function getNodeValue(obj,tag)
{
	return obj.getElementsByTagName(tag)[0].firstChild.nodeValue;
}

function changeType(http_request) {
	if (http_request.readyState == 4) 
	{
		if (http_request.status == 200) 
		{
			var selectbox = document.getElementById('selectType');
			selectbox.options.length=1;

			var type = http_request.responseXML.getElementsByTagName('type');
			
			for (var i=0;i<type.length;i++) {
				selectbox.options[selectbox.options.length]=new Option(getNodeValue(type[i],'name'),getNodeValue(type[i],'id'),false,false)
			}

		} 
		else 
		{
			alert('There was a problem with the request.');
		}
	}
}