代码

functions.php里面添加如下代码

//相关文章
function wp_related_posts($num=6){
    global $post;
    $data = array();
    $counter = 1;
    $exclude_id = get_post_meta($post->ID,'related',true);//获取手动置顶的相关文章
    if ($exclude_id){
        $args = array(
            'post_status' => 'publish',
            'post_type' => array('post'),
            'post__in' => explode(',', $exclude_id),
            'posts_per_page' => $num
        );
        $posts = get_posts($args);
        foreach($posts as $sb){
            $data[] = array(
                'id' => $sb->ID,
                'post_title' => $sb->post_title,
                'post_date' => $sb->post_date,
                'link' => get_permalink($sb->ID),
            );
            $i++;
        }
    }
    if( $i < $num){//自定义文章数不足后通过分类和标签处理
        $tagsid = array();
        $catid = array();
        $thisid[] = $post->ID;
        $posttags = get_the_tags();
        $catids = get_the_category();
        if(!empty($posttags)) {
            foreach($posttags as $tag) {
                $tagsid[] = $tag->term_id;
            }
        }
        if(!empty($catids)) {
            foreach($catids as $cat) {
                $catid[] = $cat->term_id;
            }
        }
        $args = array(
            'post_type' => 'post',
            'post__not_in' => $thisid,
            'ignore_sticky_posts' => 1,
            'posts_per_page' => ($num - $i),
            'tax_query' => array(
                'relation' => 'OR',//改成AND则必须是同标签同分类下
                array(
                    'taxonomy' => 'post_tag',
                    'field'    => 'term_id',
                    'terms'    => $tagsid,
                ),
                array(
                    'taxonomy' => 'category',
                    'field'    => 'term_id',
                    'terms'    => $catid,
                ),
            ),
        );
        $rsp = get_posts($args );
        foreach($rsp as $sb){
            $data[] = array(
                'id' => $sb->ID,
                'post_title' => $sb->post_title,
                'post_date' => $sb->post_date,
                'link' => get_permalink($sb->ID),
            );
        }
    }
    return $data;
}