php實現二級聯動菜單

<label>大類：</label>
<select name="bigname" id="bigname"> 
<option value="1">前端技術</option> 
<option value="2">程序開發</option> 
<option value="3">數據庫</option> 
</select> 
<label>小類：</label> 
<select name="smallname" id="smallname"> 
</select>

<script>
 $(function(){ 
 getSelectVal(); 
 $("#bigname").change(function(){ 
 getSelectVal(); 
 }); 
 })
function getSelectVal(){ 
 $.getJSON("server.php",{bigname:$("#bigname").val()},function(json){ 
 var smallname = $("#smallname"); 
 $("option",smallname).remove(); 
 $.each(json,function(index,array){ 
 var option = "<option > > value='"+array['id']+"'>"+array['title']+"</option>"; 
 smallname.append(option); 
 }); 
 }); 
 } 
</script>