= new XMLHttpRequest();
            xhr.open('post', url, true);
            xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');

            xhr.onreadystatechange = function () {
                if (xhr.readyState === 4) {
                    if (xhr.status === 200) {
                        successCallback();
                    } else if (errorCallback != null) {
                        errorCallback(xhr.status, xhr.statusText, xhr.responseText);
                    }
            