ajax 城市区域选择三级联动

<body onLoad="sheng()">
<div class="xqbody">
    <form action="#" method="post" class="editform">
        <p class="qychoose">工作区域选择：</p>
        <div class="namebox">
            <label>姓      名：</label>
            <select name="sheng" id='sheng'>
               <option>请选择省份</option>
            </select>
            <select name="shi" id='shi'><option>请选择城市</option></select>
            <select name="qu" id='qu'><option>请选择区域</option></select>
        </div>
    </form>
</div>
<div class="clear"></div>
<script>
   function sheng(){
       $.getJSON('/php/city.php','tid=0',function(data){
           var count = data.length;
           var html = '';
           if(count==0){return;}
           for(var i=0;i<count;i++){
               html = html+'<option value="'+data[i].name+'" t>'+data[i].name+'</option>';
           }
           $('#qu').append(html);
       });
   });
</script>