problem with xmlhttp calls

	var xmlhttp = new getXMLObject();
	var time_variable;
 
	function getXMLObject()  //XML OBJECT
	{
		var xmlHttp = false;
		try {
			xmlHttp = new ActiveXObject("Msxml2.XMLHTTP")  // For Old Microsoft Browsers
		}
		catch (e) {
			try {
				xmlHttp = new ActiveXObject("Microsoft.XMLHTTP")  // For Microsoft IE 6.0+
			}
			catch (e2) {
				xmlHttp = false   // No Browser accepts the XMLHTTP Object then false
			}
		}
		if (!xmlHttp && typeof XMLHttpRequest != 'undefined') {
			xmlHttp = new XMLHttpRequest();        //For Mozilla, Opera Browsers
		}
		return xmlHttp;  // Mandatory Statement returning the ajax object created
	}

	var name_='';
 
	function ajaxFunction(name) {
		if(xmlhttp) { 
                        $name_ = name;
			xmlhttp.open("GET","http://localhost/getage.php?name="+$name_ ,true);
			xmlhttp.onreadystatechange  = handleServerResponse;
			xmlhttp.send(null);
		}
	}
 
	function handleServerResponse() {
		if (xmlhttp.readyState == 4) {
			if(xmlhttp.status == 200) {
				document.getElementById($name_).value=xmlhttp.responseText; //Update the HTML Form element 
			}
			else {
				alert("Error during AJAX call. Please try again");
			}
		}
	}

	function getage()
	{
		ajaxFunction('Tim');
               
		ajaxFunction('Kate');
	}

PHP:

I have such code, and when I try to call the function getage(), I see many errors "Error during AJAX call. Please try again", and after clicking OK,OK..., I see only result of function ajaxFunction('Kate'), -> ie Kate's age appears in <input type='text' name='age' id='Kate'>.

I guess that, the reason is in asynchronous call of ajax - when the first function has not yet received the results, the second is beginning to be run.
So, how switch these two functions ajaxFunction('Tim') and ajaxFunction('Kate')? Please help.