If you check out the source of _wp_link_page, you’ll see all the URL calculations are coded directly within – you can either lift this code straight out into your own function, or sprinkle a little regex around the existing function: function wpse_204737_get_post_page_url( $i ) { if ( preg_match( ‘/href=”https://wordpress.stackexchange.com/questions/204737/([^”]+)”https://wordpress.stackexchange.com/”, _wp_link_page( $i ), $match ) ) … Read more
Best solution for what you want to accomplish which is essentially to make the next page feature more user friendly for your authors is to add a TinyMCE button that will do this for you. This may be a bit complicated so hold your hat. To avoid this answer being the length of a thesis, … Read more
UPDATE 21-01-2016 19:35 SA TIME – BUG FOUND!!!!! YEAH!!!!!! I finally found the bug. As you stated in your last update, the failure only happens when $post_content has a <!–nextpage–> tag in the content. I tested it, and did confirm that any other page after the page after the <!–nextpage–> returns a 404 and then … Read more