我需要获得自定义帖子类型的相关帖子。这只适用于post。但对于自定义帖子类型不显示任何内容，因为wp\\u get\\u post\\u categories（$id）未返回任何内容。

$related = get_posts( array( \'category__in\' => wp_get_post_categories($id), \'numberposts\' => $post_num, \'post__not_in\' => array($id) ) );

$category = get_the_terms( $id, \'cases\' );
    $cat = array(); 
    if($category){
        $cat[] = $category->term_id;
    }
    $related = get_posts( array( \'category__in\' => $cat, \'numberposts\' => $post_num, \'post__not_in\' => array($id) ) );