ช่วยดูโค๊ด Dropdownlist class 2 ชั้น ให้หน่อยนะครับ

//function Dropdownlist(){
function dropdownlist(listindex)
{

document.formname.subcategory.options.length = 0;
switch (listindex)
{
<?
$sql_="select * from jos_sections";
$re_=mysql_query($sql_);
while ($data_=mysql_fetch_array($re_)){
 ?>
case "<?=$data_[id]?>" :
<? 
$sql_1="select * from jos_categories where section=$data_[id]";
$re_1=mysql_query($sql_1);
$i=0;
while ($data_1=mysql_fetch_array($re_1)){
?>
document.formname.subcategory.options[<?=$i?>]=new Option("<?=$data_1[title]?>","");
<? $i++;
}?>
break;
<? }?>
}
return true;
}
</script>
</head>
<? 
$sql="select * from jos_sections";
$re=mysql_query($sql);
?>
<form id="formname" name="formname" method="post" action="submitform.asp" >
<table width="50%" border="0" cellspacing="0" cellpadding="5">
<tr>
<td width="41%" align="right" valign="middle">Category :</td>
<td width="59%" align="left" valign="middle"><select name="category" id="category" onchange="javascript: dropdownlist(this.options[this.selectedIndex].value);">
<option value="">:: Select Category ::</option>
<? while ($data=mysql_fetch_array($re)){?>
<option value="<?=$data[id]?>"><?=$data[title]?></option>
<? }?>
</select></td>
</tr>
<tr>
<td align="right" valign="middle">Sub Category :
</td>
<td align="left" valign="middle"><script type="text/javascript" language="JavaScript">
document.write('<select name="subcategory"><option value="">Select Sub-Category</option></select>')
</script>
<noscript><select name="subcategory" id="subcategory" >
<option value="">:: Select Sub-Category ::</option>
</select>
</noscript>