给WordPress 自带的搜索功能添加过滤只搜索文章的标题

如果想让 WordPress 自带的搜索功能只搜索文章标题，让搜索结果更加精确（其实WordPress 自带的搜索功能本来模糊查找就很弱），可以将下面的代码添加到当前主题functions.php中：

// 只搜索文章标题
function wpse_11826_search_by_title( $search, $wp_query ) {
    if ( ! empty( $search ) && ! empty( $wp_query->query_vars['search_terms'] ) ) {
        global $wpdb;
        $q = $wp_query->query_vars;
        $n = ! empty( $q['exact'] ) ? '' : '%';
        $search = array();
        foreach ( ( array ) $q['search_terms'] as $term )
            $search[] = $wpdb->prepare( "$wpdb->posts.post_title LIKE %s", $n . $wpdb->esc_like( $term ) . $n );
        if ( ! is_user_logged_in() )
            $search[] = "$wpdb->posts.post_password = ''";
        $search = ' AND ' . implode( ' AND ', $search );
    }
    return $search;
}
add_filter( 'posts_search', 'wpse_11826_search_by_title', 10, 2 );