你需要获得CPT (Custom Post Type) A, 然后在第二个循环CPT 在CPT的元数据库中B.示例：

$my_titles = array(
    \'post_status\' => \'publish\',
    \'posts_per_page\' => -1,
    \'order\' => \'ASC\',
    \'post_type\' => \'my_custom_post_type\' // get the type of your CPT
);

    <select name="" id="">
        <?php foreach ($my_titles as $key => $title): ?>
            <option value=""><?php echo $title; ?></option>
        <?php endforeach ?>
    </select>