vasvirshich

We want to see the post update date for single pages. And in the archives – the date the last post was updated.

It’s easier to make a hook that will allow you to override the sending of Last-modified headers.

Send to last-modified the time the post was created or modified

Just for example:

/**
 * If posts, pages, custom post types
 */
if ( is_singular() ) {
    global $post;

    if ( ! isset($post->post_modified_gmt) ) {
        return;
    }

    $post_time = strtotime( $post->post_modified_gmt );
    $modified_time = $post_time;

    /**
     * If we have comment set new modified date
     */
    if ( (int) $post->comment_count > 0 ) {
        $comments = get_comments( array(
            'post_id' => $post->ID,
            'number' => '1',
            'status' => 'approve',
            'orderby' => 'comment_date_gmt',
        ) );
        if ( ! empty($comments) && isset($comments[0]) ) {
            $comment_time = strtotime( $comments[0]->comment_date_gmt );
            if ( $comment_time > $post_time ) {
                $modified_time = $comment_time;
            }
        }
    }

    $last_modified = str_replace('+0000', 'GMT', gmdate('r', $modified_time));

}

We can modify cache.php to suit our needs. But when updating the plugin, the changes will be lost.
Maybe there is some way to avoid this?