var xmlHttp, frm;

function GetXmlHttpObject(){ 
	var objXMLHttp=null
	if (window.XMLHttpRequest)
	{
	objXMLHttp=new XMLHttpRequest()
	}
	else if (window.ActiveXObject)
	{
	objXMLHttp=new ActiveXObject("Microsoft.XMLHTTP")
	}
	return objXMLHttp
}


function checkLogin(obj)
	{ 
		frm = obj;
		var u = frm.u.value;
		var p = frm.p.value;
		
			
		
		xmlHttp=GetXmlHttpObject();
		if (xmlHttp==null)
		  {
		  alert ("Your browser does not support AJAX!");
		  return;
		  }
		var url="doLoginXML.php";
		//var url = "phptest.php";
		url=url+"?u="+u+"&p="+p;
		//url=url+"&sid="+Math.random();

		 
		xmlHttp.onreadystatechange=loginStateChanged;
		xmlHttp.open("GET",url,true);
		xmlHttp.setRequestHeader("Content-type", "text/xml");
		xmlHttp.send(null);
		
		return false;
	}
		
		
	function loginStateChanged(){ 
		if (xmlHttp.readyState==4){

			var elt = document.getElementById('msg');
		
			var xmlDoc=xmlHttp.responseXML.documentElement;
			//var xmlDoc=xmlHttp.responseText;
			var res='';
			var code = xmlDoc.getElementsByTagName("code")[0].childNodes[0].nodeValue;
			
			if(code=='u'){
				
				res ='Username is incorrect';
				
			}else if(code=='p'){
				res='Password is incorrect';
			
			}else if(code=='z'){
				res='You have entered incorrect details, please try again.';
		
			}else{		
				// should go back to the referer
				window.location.href= frm.ref.value;
			}
			
			elt.innerHTML= "<p>"+res+"</p>";
			if(res!=''){
				elt.style.display="block";
			}

		}
	}