select 修改时 选择默认值

<tr>
  <td align="right" height="18">选择品种：</td>
  <td align="left">
<select name="arr[pinid]" id="pinid">
<option value="84" name="arr[pinid]">建材</option>
<option value="127" name="arr[pinid]">热轧</option>
<option value="86" name="arr[pinid]">中厚板</option>
</select>
  </td>
</tr>
<tr>
<td align="right" height="18">选择地区：</td>
<td align="left">
<select name="arr[areaid]" id="areaid">
<option value="all">全部</option>
<?php echo $list_area?>
</select>
</td>
</tr>

$(document).ready(function(){
$("#pinid  option[value='<?php echo $arr['pinid'];?>']").attr("selected",true);
$("#areaid  option[value='<?php echo $arr['areaid'];?>']").attr("selected",true);
});