Ajax实现评论提交

http();
        if(!xmlhttp)
        {alert("你的浏览器不支持XMLHTTP！！");
            return;
        }
        showloading() 
        xmlhttp.onreadystatechange=requestdata;
        xmlhttp.open("GET",url,true);
        xmlhttp.send(null);
        function requestdata()
        {        fopen(obj1);
                //echo(obj1,"正在加载数据，请稍等......");
                //alert(xmlhttp.readyState)
                if(xmlhttp.readyState==4)
                {    if(xmlhttp.status==200)
                    {    if(obj1!=obj2){fclose(obj1);};
                        echo(obj2,xmlhttp.responseText);
                        showloading() 
                    }
                }            
        }
}
function postdata(url,obj,data)
{       var rnd=Math.random()
        var xmlhttp=createxmlhttp();
        if(!xmlhttp)
        {
            alert("你的浏览器不支持XMLHTTP！！");
            return;
        }
        showloading() 
        xmlhttp.open("POST", url, true);
        xmlhttp.onreadystatechange=requestdata;