链接选择子板

I've written this code:

<select id="board_id" name="board_id" class="select_class">
<?php $userId  = $this->session->userdata('login_user_id');?>
<?php $userBoards   = getUserBoard($userId);?>
<?php foreach ($userBoards as $boardKey => $boardValues):?>
<option value="<?php echo $boardValues->id;?>"><?php echo $boardValues->board_name;?>    </option>
<?php endforeach;?>
</select>

It logs the user and displays a dropdown list of that users boards. I have sub-boards too. It displays them all. I'm trying to modify this code to display just sub-boards, or at least mark sub-boards differently so the user knows which is which. Currently it lists them all by time of creation, regardless of board/sub-board status.

The column in SQL which tells me if the board is sub or not is sub. If the board is sub the id of the parent board is the value in this column $boardValues->id.

I originally wanted chained select to do this but it was too difficult to grasp and wouldn't work on my website.

you can use optgroup html tag to differentiate between boards and sub-boards.

see example

In other way you can use text-indent style for sub-boards option to display differently.