原生JS Ajax 提交post表单信息

            var xmlhttp;
            if (window.XMLHttpRequest)
              {// code for IE7+, Firefox, Chrome, Opera, Safari
              xmlhttp=new XMLHttpRequest();
              }
            else
              {// code for IE6, IE5
              xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
              }
            xmlhttp.onreadystatechange=function()
              {
              if (xmlhttp.readyState==4 && xmlhttp.status==200)
                {
                    sl('block',1);
                //document.getElementById("opt").style='block';
                //alert(xmlhttp.responseText);
                }
              }
            xmlhttp.open("POST","/dota/wenjuan",true);
            xmlhttp.setRequestHeader("Content-type","application/x-www-form-urlencoded");
            xmlhttp.send("answer1="+answer1+"&answer2="+answer2+"&answer3="+answer3+"&answer4="+answer4+"&answer5="+answer5+"&answer6="+answer6+"&answer7="+answer7+"&answer8="+answer8+"&answer9="+answer9+"&answer10="+answer10+"&gameid="+gameid+"&phone="+phone+"&type="+type);

php端代码正常$_POST 使用  ，返回给ajax数据信息用echo  ..然后exit;