var http_request = false;
function send_request(method, url, content, responseType, callback) {

    http_request = false;
    if (window.XMLHttpRequest) {
        http_request = new XMLHttpRequest();
        if (http_request.overrideMimeType) {
            http_request.overrideMimeType("text/xml");
        }
    }
    else if (window.ActiveXObject) {
        try {
            http_request = new ActiveXObject("Msxml2.XMLHTTP");
        } catch(e) {
            try {
                http_request = new ActiveXObject("Microsoft.XMLHTTP");
            } catch(e) {
            }
        }
    }

    if (!http_request) {
        window.alert("不能创建XMLHttpRequest对象实例。");
        return false;
    }

    if (responseType.toLowerCase() == "text") {
        http_request.onreadystatechange = callback;
    }
    else if (responseType.toLowerCase() == "xml") {
        http_request.onreadystatechange = callback;
    }
    else {
        window.alert("响应类别参数错误。");
        return false;
    }

    if (method.toLowerCase() == "get") {
        http_request.open(method, url, true);
    }
    else if (method.toLowerCase() == "post") {
        http_request.open(method, url, true);
        http_request.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
    }
    else {
        window.alert("http请求类别参数错误。");
        return false;
    }
    http_request.send(content);

}

function processTextResponse() {
    if (http_request.readyState == 4) {
        if (http_request.status == 200) {
            alert("Text 文档响应。");
        } else {
            alert("您所请求的页面有异常。");
        }
    }
}

function processXMLResponse() {
    if (http_request.readyState == 4) {
        if (http_request.status == 200) {
            alert("XML 文档响应。");
        } else {
            alert("您所请求的页面有异常。");
        }
    }
}