json数据返回

<script type="text/javascript">
function xmlpage(){
    var xhr=new XMLHttpRequest();
    xhr.onreadystatechange=function(){
        if(xhr.readyState===4){
            eval("var obj="+xhr.responseText);
            var str="地址"+obj.weatherinfo.city+"温度"+obj.weatherinfo.temp+"风向"+obj.weatherinfo.WD;
            document.getElementById("tq").innerHTML=str;
            }
        }
    xhr.open("GET","/6.php");
    xhr.send(null);
    }
window.onload=function(){
    xmlpage();};
</script>
<div id="tq"></div>

<?php
echo '{"weatherinfo":{"city":"北京","cityid":"101010100","temp":"10","WD":"东南风","WS":"2级","SD":"26%","WSE":"2","time":"10:25","isRadar":"1","Radar":"JC_RADAR_AZ9010_JB","njd":"暂无实况","qy":"1012"}}';
?>