here's my example:

HTML Code:
var string = "  sh*t ajax";
xmlhttp.onreadystatechange = TransResp;
xmlhttp.open("POST",url,true);
xmlhttp.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
	xmlhttp.send(
		"string="+string
	);
	return true;
And here's my resuld $_POST["string"] is blank ???

and only when i change my string become: "shi*t ajax"; then POST string return exactly value

i don't know what's going on with XMLHttpRequest ???