这个问题比你想象的要复杂得多。

尽管如此（或者真的，因为它），我还是要尝试一下。。。

add_metabox(\'terms-post-selector\',\'Select Related Post\',\'post_terms_selector_dropdown\',null,\'post\',\'side\',\'high\');

function post_terms_selector_dropdown() {

    global $post;
    $taxonomy = \'property_type\'; // or whatever it is
    $terms = get_the_terms($postid,$taxonomy);
    $selectedterm = get_post_meta($post->ID,\'_selected_term\',true);

    if (count($terms) > 0) {
        echo "<select name=\'termselector\' id=\'termselector\' onchange=\'loadpostterms();\'>";
        foreach ($terms as $term) {
            echo "<option value=\'".$term->value."\'";
            if ($term->value == $selectedterm) {echo " selected=\'selected\'";}
            echo ">".$term->name."</option>";
        }
        echo "</select>";

        echo "<div id=\'posttermselecter\'></div>";
    }

    // javascript to trigger the AJAX creation of post dropdown select element
    echo "<script>function loadpostterms() {
        var ajaxurl = \'".admin_url(\'admin-ajax.php\')."\';
        var termselector = document.getElementById(\'termselector\');
        var selectedterm = termsselector.options[termselector.selectedIndex].value;
        document.getElementByID(\'termqueryiframe\').src = ajaxurl+\'?action=post_terms_dropdown&term=\'+selectedterm+\'&postid=".$post->ID."\';
    </script>";

    // just a dummy iframe to handle the AJAX post selector callback
    echo "<iframe src=\'javascript:void(0);\' id=\'termqueryiframe\' style=\'display:none;\'></iframe>";

}


// AJAX callback to populate the post select element
add_action(\'wp_ajax_post_terms_dropdown\',\'post_terms_dropdown\');
add_action(\'wp_ajax_nopriv_post_terms_dropdown\',\'post_terms_dropdown\');
function post_terms_dropdown() {

    // get all posts with specified term
    $term = $_GET[\'term\'];
    $taxonomy = \'property_type\'; // or whatever it is
    $args = array(\'tax_query\' => array(array(
    \'taxonomy\' => $taxonomy, \'field\' => \'ID\', \'terms\' => $term
    ) ) );
    $posts = get_posts($args);

    if (count($posts) > 0) {
        // get the currently selected post
        $postid = $_GET{\'postid\'];
        $selectedpost = get_post_meta($postid,\'_selected_post\',true);

        // create the post dropdown and send it back to parent frame
        echo "<script>var postselector = \'<select name=\\"posttermselector\\">\';";
        foreach ($posts as $post) {
            echo "postselector += \'<option value=\\"".$post->ID."\\"";
            if ($post->ID == $selectedpost) {echo " selected=\\"selected\\"";}
            echo ">".$vpost->post_title."</option>\';";
        }
        echo "postselector += \'</select>\';
        parent.document.getElementById(\'posttermselector\').innerHTML = postselector;</script>";
   }
   exit;
}

// update the hidden post fields on post publish / save
add_action(\'publish_post\',\'select_post_terms_update\');
add_action(\'save_post\',\'select_post_terms_update\');

function select_post_terms_update($postid) {

    if (defined(\'DOING_AUTOSAVE\') && DOING_AUTOSAVE) {return;}
    if (!current_user_can(\'edit_post\',$postid)) {return;}

    if (isset($_POST[\'termselector\'])) {
        update_post_meta($postid,\'_selected_term\',$_POST[\'termselector\']);
    }
    if (isset($_POST[\'posttermselector\'])) {
        update_post_meta($postid,\'_selected_post\',$_POST[\'posttermselector\']);
    }

}

请注意，这个网络的政策并不是像我在这里所做的那样鼓励他人“为你做你的工作”——我只是想做一些有趣的事情，这个问题问得很好。祝你好运，我希望它对你有用！（没有像这样从头开始写的担保。）