function getXMLHttpRequest() {
    if(window.ActiveXObject) {
        try {
            return new ActiveXObject("Msxml2.SMLHTTP");
        }
        catch (e) {
            try {
                return new ActiveXObject("Microsoft.XMLHTTP");
            }
            catch (e1) {
                return null;
            }
        }
    }
    else if(window.XMLHttpRequest) {
        return new XMLHttpRequest();
    }
    else {
        return null;
    }
}

var httpRequest = null;

function sendRequest(url, params, callback, method) {
    httpRequest = getXMLHttpRequest();
    var httpMethod = method ? method : 'GET';

    if(httpMethod != 'GET' && httpMethod != 'POST') {
        httpMethod = 'GET';
    }

    var httpParams = (params == null || params == '') ? null : params;
    var httpUrl = url;

    if(httpMethod == 'GET' && httpParams != null) {
        httpUrl = httpUrl + "?" + httpParams;
    }

    httpRequest.open(httpMethod, httpUrl, true);
    httpRequest.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
    httpRequest.onreadystatechange = callback;
    httpRequest.send(httpMethod == 'POST' ? httpParams : null);
}