grouping sub kategory list

<?php
// query data from database
$pilihan=mysql_query(
    "SELECT a.id_sub_kategori,b.id_kategori,b.nama_kategori,a.nama_subkategori
     FROM subkategori a INNER JOIN kategori b ON a.id_kategori=b.id_kategori
     WHERE b.aktif='Y'
     ORDER BY b.id_kategori,a.id_subkategori"
);
// store given data to an array
$opts=array();
while($r=mysql_fetch_array($pilihan)){
  $opts[]=$r;
}
$its_group=0;// its option new group?
$group='';   // group label
// build a list of options
?>
<select name="subkategori>
<option value="0" selected="selected">-- pilih kategori</option>
<?php
for($i=0;$i<count($opts);$i++){
  if($group==''|| $group!=$opts[$i]['nama_kategori']){
    $group=$opts[$i]['nama_kategori'];
    $its_group=1;
    echo "<optgroup label=\"".$opts[$i]['nama_kategori']."\">\n"
  }
  echo "<option value=\"".$opts[$i]['id_subkategori']."\">"
      .$opts[$i]['nama_subkategori']
      ."</option>\n";
  if($its_group){
    echo "</optgroup>\n";
    $its_group=0;
  }
}
?>
</select>