你必须使用the_content 和the_excerpt_rss 挂钩。您可以这样做：

function rss_append_footer($content) {
    if(is_feed()) {
        $related_posts_html = ...  // I assume you already can compute it
        $content .= $related_posts_html;
    }
    return $content;
}

add_filter(\'the_content\', \'rss_append_footer\');
add_filter(\'the_excerpt_rss\', \'rss_append_footer\');