close comments after days

/**
 * Close comments on old posts on the fly, without any extra DB queries.  Hooked to the_posts.
 *
 * @access private
 * @since 2.7.0
 *
 * @param object $posts Post data object.
 * @return object
 */
function _close_comments_for_old_posts( $posts ) {
    if ( empty($posts) || !is_singular() || !get_option('close_comments_for_old_posts') )
        return $posts;

    $post_types = apply_filters( 'close_comments_for_post_types', array( 'post' ) );
    if ( ! in_array( $posts[0]->post_type, $post_types ) )
        return $posts;

    $days_old = (int) get_option('close_comments_days_old');
    if ( !$days_old )
        return $posts;

    if ( time() - strtotime( $posts[0]->post_date_gmt ) > ( $days_old * 24 * 60 * 60 ) ) {
        $posts[0]->comment_status = 'closed';
        $posts[0]->ping_status = 'closed';
    }

    return $posts;
}