Recently Updated Posts Shortcode

add_action( 'init', function () {
    add_shortcode( 'recently_updated', function ( $atts ) {
        $atts = shortcode_atts( array( 'count' => 5, 'post_type' => 'post' ), $atts, 'recently_updated' );

        $cache_key = 'wpide_recent_upd_' . md5( wp_json_encode( $atts ) . get_option( 'wpide_recent_upd_ver', '1' ) );
        $html      = get_transient( $cache_key );
        if ( false !== $html ) {
            return $html;
        }

        global $wpdb;
        $types = array_filter( array_map( 'sanitize_key', explode( ',', $atts['post_type'] ) ) );
        $in    = implode( ',', array_fill( 0, count( $types ), '%s' ) );
        $ids   = $wpdb->get_col( $wpdb->prepare(
            "SELECT ID FROM {$wpdb->posts} WHERE post_status = 'publish' AND post_type IN ($in) AND post_password = ''
            AND post_modified_gmt > DATE_ADD(post_date_gmt, INTERVAL 1 DAY) ORDER BY post_modified_gmt DESC LIMIT %d",
            array_merge( $types, array( max( 1, min( 20, (int) $atts['count'] ) ) ) )
        ) );

        $html = '';
        if ( $ids ) {
            _prime_post_caches( $ids, false, false );
            $html = '<ul class="wpide-recently-updated">';
            foreach ( $ids as $id ) {
                $html .= sprintf(
                    '<li><a href="%s">%s</a> <small>updated <time datetime="%s">%s</time></small></li>',
                    esc_url( get_permalink( $id ) ),
                    esc_html( get_the_title( $id ) ),
                    esc_attr( get_post_modified_time( 'c', true, $id ) ),
                    esc_html( get_the_modified_date( '', $id ) )
                );
            }
            $html .= '</ul>';
        }

        set_transient( $cache_key, $html, HOUR_IN_SECONDS );
        return $html;
    } );
} );

// A new version number makes every cached list stale at once.
add_action( 'save_post', function ( $post_id, $post ) {
    if ( 'revision' !== $post->post_type && 'auto-draft' !== $post->post_status ) {
        update_option( 'wpide_recent_upd_ver', (string) time(), false );
    }
}, 10, 2 );