Hi @hummelmose
Thanks for the clarification. This is how I would do it.
Add an action to the wp action. This action is run when WP is ready to function.
Look at the URL (find the url in the $_SERVER array) and check if the url follows your above pattern. You can check for a patern with regexp.
After the matching is done and you have a variable holding the $article_id, your next step is to find the post that has a matching custom field value.
You can query the WP posts with teh get_posts function as shown here:
http://www.advancedcustomfields.com/resources/how-to/how-to-query-posts-filtered-by-custom-field-values/
Then, once you have the $post object, you can redirect to it like so:
wp_redirect( get_permalink( $post->ID ) );
exit;
I hope the above makes sense. You may need to get some help from a PHP / WP dev if you can’t get it to work.
Good luck mate.
Cheers
E
