WordPress如何按标题匹配搜索结果

WordPress的搜索结果是匹配文章或页面的标题和内容，在一些情况下，这个显示有点多余，故此有了搜索只匹配标题的功能。那么如果WordPress想按标题匹配搜索结果，加什么代码呢？

复制以下代码到主题的 functions.php 文件最后即可。

add_filter('posts_search', 'tbwp_search_by_title_only', 500, 2);
function tbwp_search_by_title_only($search) {
    global $wpdb, $wp_query;
    if (empty($search))
        return $search;
    $q = $wp_query->query_vars;
    $n = !empty($q['exact']) ? '' : '%';
    $search =
        $searchand = '';
    foreach ((array) $q['search_terms'] as $term) {
        $term = esc_sql($wpdb->esc_like($term));
        $search .= "{$searchand}($wpdb->posts.post_title LIKE '{$n}{$term}{$n}')";
        $searchand = ' AND ';
    }
    if (!empty($search)) {
        $search = " AND ({$search}) ";
        if (!is_user_logged_in())
            $search .= " AND ($wpdb->posts.post_password = '') ";
    }
    return $search;
}