这里的问题很简单Display list of tags as drop down menu or radio buttons in a meta box?

但您需要查询旅行者的邮件列表，而不是标签列表，邮件类型如下：

$travelers = new WP_Query();
$travelers ->query(\'post_type=travelers&postprepage=-1\');
while ($travelers->have_posts()) : 
   $recentPosts->the_post();
   $travellersnames[] = $post->title;
endwhile

根据我的答案

$s_query = new WP_Query( array(
    \'suppress_filters\' => false,
    \'post_type\' => \'slide\'));
while($s_query->have_posts()):$s_query->the_post();

    $sname = $post->post_title;
    $s_output2 =\'\';
    $s_output2 .= \'<option value="\'.$post->ID.\'" >\';
    $s_output2 .= $post->post_title;
    $s_output2 .= \'</option>\';
    echo $s_output2;

endwhile ;
wp_reset_query();