readyState does not get past 1

试图通过javascripts open（）函数将数据放入XML中
但该网站无法通过readyState 1，
下面是Java脚本代码

function addItem()
{
    var name = document.getElementById('Iname').value;
    var price = document.getElementById('Iprice').value;
    var quantity = document.getElementById('Iquantity').value;
    var description = document.getElementById('Idescription').value;
    xHRObject.open("GET", "listing.php", true);
    xHRObject.onreadystatechange = function() {
        if (xHRObject.readyState == 4 && xHRObject.status == 200)
        {
            document.getElementById('Information').innerHTML = xHRObject.responseText;
            xHRObject.send(null);
        } 
    }
}

我不知道这是否是PHP的错误，但它相当大，所以我只会在需要时发布它。