说明：前几天发了个无需插件给博客网站添加一言功能的方法，参考：给博客网站添加Hitokoto - 一言经典语句功能，现在再发个不需要插件给WordPress网站添加“历史上的今天”功能的方法。这样可以很好清楚的知道，历史的同一天发过什么文章。

方法

在模板的function.php最下面，也就是“?>”之前添加下面代码即可实现：

function wp_history_post_base($post_year, $post_month, $post_day){
    global $wpdb;
    $limit = 30;
    $order = "latest";
    if($order == "latest"){ $order = "DESC";} else { $order = '';}
    $sql = "select ID, year(post_date_gmt) as h_year, post_title, comment_count FROM 
    $wpdb->posts WHERE post_password = '' AND post_type = 'post' AND post_status = 'publish'
    AND year(post_date_gmt)!='$post_year' AND month(post_date_gmt)='$post_month' AND day(post_date_gmt)='$post_day'
    order by post_date_gmt $order limit $limit";
    $histtory_post = $wpdb->get_results($sql);
    return $histtory_post;
}
 
function wp_history_post_single(){
    $wp_history_post_content_list = '<p>%YEAR%年：<a href="%LINK%" title="%TITLE%" rel="external nofollow">%TITLE%（%COMMENTS_NUM%条评论）</a></p>';
    $wp_history_post_content_title = '<h3>历史上的今天</h3>';
    $histtory_post = wp_history_post_base(get_the_time('Y'), get_the_time('m'), get_the_time('j'));
    if($histtory_post){
        foreach( $histtory_post as $post ){
            $h_year = $post->h_year;
            $h_post_title = $post->post_title;
            $h_permalink = get_permalink( $post->ID );
            $h_comments = $post->comment_count;
            $h_post .= $wp_history_post_content_list;
            $h_post = str_replace("%YEAR%", $h_year, $h_post);
            $h_post = str_replace("%LINK%", $h_permalink, $h_post);
            $h_post = str_replace("%TITLE%", $h_post_title, $h_post);
            $h_post = str_replace("%COMMENTS_NUM%", $h_comments, $h_post);
        }
    }
    if($h_post){
        $result = $wp_history_post_content_title.$h_post;
    }
    return $result;
    wp_reset_query();
}
 
function wp_history_post_content($content){
    global $wpdb;
    if(is_single()){
        $content .= wp_history_post_single();
    }
    return $content;
}
add_action('the_content', 'wp_history_post_content');