正确的ajax发布语法？

Hello I'm trying to post data to a database and it's working with get, but not with post.

Here's my javascript:

function updateShout(id)
{
    var http = new XMLHttpRequest();
    http.open("POST", location.href);
    http.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    http.send("edit="+document.getElementById("EDITM").value+"&id="+id);
    return false;
}

I'm making an ajax request to the current page with: index.php?edit=message&id=X

PHP is working fine, but I believe it's something with this line:

http.send("edit="+document.getElementById("EDITM").value+"&id="+id);

PHP (if needed):

if($_SESSION['signedin'])
{
    if(!is_blank($_REQUEST['edit'])) //if empty($value) && !is_numeric($value);
    {
        $id = toNum( $_REQUEST['id'] ); //if(!is_numeric($val)) return -1; return (int)$val;
        $msg = htmlentities($_REQUEST['edit']); //secure dis
        $query = $db->query("UPDATE shouts SET shout='$msg' WHERE shoutid='$id'");
        $db->close();
        exit;
    }
}

please close.. found my issue. my had name instead of id as "EDITM"