Rewrite rule : custom post type with 2 numeric variiables

Question

I have a wordpress site using a custom post type "gallery" to show some photos. I can't find the right regex to match my url variables (i'm a novice with regex)

What i want to achieve is to get this form of url :

/custom_post_type_slug/custom_post_type_name/page_num/photo_id/

in my case it should give :

/gallery/name-of-gallery/1/15/

I've tried this regex :

add_rewrite_rule( 'gallery/(.+?)(?:/([0-9]+))?/([0-9]{1,2})/([0-9]{1,2})/?$', 'index.php?gallery=$matches[1]&page=$matches[2]&photo=$matches[3]','top' );

with no success.

When I test this rewrite rule with Query Monitor it tells that photo=$matches[3] and page is null.

If someone could give me an advise it will be very nice.

Answer 1

add_rewrite_rule() cannot automatically create that permalink structure for you. You should use wp_link_pages_link filter. E.g:

add_filter('wp_link_pages_link', function($link, $i)
{
  global $post, $photo_id;

  if ($photo_id && 'gallery' === $post->post_type)
    $link = $link . '/' . intval($photo_id) . '/';

  return $link;
}, PHP_INT_MAX, 2);

Then, you must use add_rewrite_tag() to make WordPress aware of photo query string:

add_action('init', function()
{
  add_rewrite_tag('%photo%', '([0-9]+)');
  add_rewrite_rule('^gallery/([^/]+)/([0-9]+)/([0-9]+)/?$', 'index.php?post_type=gallery&name=$matches[1]&page=$matches[2]&photo=$matches[3]', 'top');
}, 0, 0);