您发布的函数使用了一个讨厌的自定义SQL查询，这实际上是不必要的，添加一个类别过滤器会使情况更糟，您可以使用WP_Query 对象或get_posts 除了排除受密码保护的帖子，这可以通过连接到posts_where 过滤，这样你就可以：

//function to exclude password protected posts
function exclude_pw_where($where) {
    $where .= " AND post_password = \'\' ";
    return $where;
}

// function to get latest posts of category
function latest_posts_of_category($no_posts = 5, $before = \'<li>\', $after = \'</li>\', $hide_pass_post = true, $skip_posts = 0, $show_excerpts = false, $include_pages = false, $cat_id = null){
    global $post;
    $temp = $post;
    $args = array(
        \'posts_per_page\' => $no_posts,
        \'post_type\' => \'post\',
        \'post_status\' => \'published\',
        \'order\' => \'DESC\',
        \'orderby\' => \'date\',
        \'offset\' => $skip_posts,
    );

    if ( $cat_id != null )
        $args[\'cat\'] = $cat_id;     

    if ( $include_pages )
        $args[\'post_type\'] = array(\'post\',\'page\');

    //add filter to exclude password protected posts
    if ( $hide_pass_post )
        add_filter(\'posts_where\', \'exclude_pw_where\');

    $posts = get_posts($args);
    if ( $posts ) {
        foreach ( $posts as $post ) {
            $post_title = $post->post_title;
            $permalink = get_permalink( $post->ID );
            $date=date(\'F j, Y\', strtotime($post->post_date));
            $output .= $before . \'<span class="date">\'.$date.\'</span><a href="\' . esc_url( $permalink ) . \'" rel="bookmark" title="Permanent Link: \' . esc_attr( $post_title ) . \'">\' . esc_html( $post_title ) ;
            if ( $show_excerpts ) {
                $post_excerpt = esc_html( $post->post_excerpt );
                $output.= \'<br />\' . $post_excerpt;
            }
            $output .= $after;
        }
    } else {
        $output .= $before . "None found" . $after;
    }
    echo $output;

    //remove the filter if was called
    if ( $hide_pass_post )
        remove_filter(\'posts_where\', \'exclude_pw_where\');

}

它也可以做同样的事情，但要安全得多，您可以设置最后一个参数$cat\\u id，以通过类别id指定类别（或使用数组的类别列表）。