将自定义字段添加到wordpress搜索检索范围中

add_action('posts_search', function($search, $query){
    global $wpdb;

    if ($query->is_main_query() && !empty($query->query['s'])) {

        $sql    = " OR EXISTS (SELECT * FROM {$wpdb->postmeta} WHERE post_id={$wpdb->posts}.ID and meta_key = 'product_no' and meta_value like %s)";
        $like   = '%' . $wpdb->esc_like($query->query['s']) . '%';

        $search .= $wpdb->prepare($sql, $like);
    }
    return $search;
},2,2);