Cannot send message using POST

[Donotalo]

The ajax code:

var xmlHttp = GetXmlHttpObject();
if (xmlHttp == null) {
	window.alert("Your browser does not support ajax.\n Please use latest version of your browser.");
	return;
}

if (xmlHttp.overrideMimeType)
	xmlHttp.overrideMimeType("text/xml");

xmlHttp.open("POST", "signup_server.php", true);
xmlHttp.setRequestHeader("Content-Type",
					"application/x-www-form- urlencoded; charset=UTF-8");
var str = "name=n";
xmlHttp.send(str);

xmlHttp.onreadystatechange = function() {
	if (xmlHttp.readyState == 4) {
		if (xmlHttp.status == 200) {
			window.status = xmlHttp.responseText;
		}
		else
			window.alert("Error " + xmlHttp.status + ": " + xmlHttp.statusText);
	}
}

Server side code:

<?php

if (isset($_POST["name"]))
	echo $_POST["name"];
else
	echo "Name not found.";
?>

After execution, the window.status contains "Name not found." string. Why the server cannot get the name=n? I'm using IIS in Windows XP SP2 and PHP version 5.2.5.

Thanks in advance.