Multiple permalinks for a single post with multiple taxonomies

I may transfer all my taxonomies as categories and it will work but I’ll come with a huge amount of categories and by the way, these taxonomies were specific to a custom post type… so now i would have the whole categories for both (posts and custom post types) which would be confusing, no ?
please any help or advice ?

Finally i came up with this :

function multiple_taxonomy_post_link($CPT_url = '')
{
  // check permalink structure for the required construct; /%category%/%postname%/
  if (strrpos(get_option('permalink_structure'), '%category%/%postname%') !== false)
  {
    // get the current post
    global $post, $wp_query;

    // prepare variables for use below
    $post_id = $term_id = 0;
    $new_CPT_url = ''; 

    // for taxonomies
    if (is_tax())
    {
      // remember current category and post
      $term_obj = get_term_by( 'slug', get_query_var( 'term' ), get_query_var( 'taxonomy' ) );
      $term_id = $term_obj->term_id;
      $post_id = $post->ID;

      // add the post slug to the current url
      $new_CPT_url = $_SERVER['REQUEST_URI'] . $post->post_name;
    }

    else if (is_singular('projects'))
    {
      // last part in the 'category_name' should be the slug for the current category
      $term_object = get_term_by( 'slug', get_query_var( 'term' ), get_query_var( 'taxonomy' ) );

      // remember current category and post
      $post_id = $wp_query->post->ID;
      if ($term_object) $term_id = $term_object->term_id;

      // replace the slug of the post being viewed by the slug of $post
      $new_CPT_url = $_SERVER['REQUEST_URI'].$post->post_name;
    } 

    if ($post_id > 0 && $term_id > 0 && !empty($new_CPT_url))
    {
    	$current_tax = get_query_var( 'taxonomy' );
    	$terms = get_the_terms( $post->ID, $current_tax );
      // make sure categories match!
      foreach($terms as $term)
      {
        if ($term->term_id == $term_id)
        {
          $CPT_url = $new_CPT_url;
          break;
        }
      }
    }

  }   

  // always return an url!
  return $CPT_url;
}
add_filter('post_type_link', 'multiple_taxonomy_post_link');

Different permalinks are pointing well to the same single post (no 404) but WP keeps rewriting at least ‘my-site/projects/post_name’. Where may i have to look to force WP to keep both url ?
cheers

anyone ?

thanks everyone i made it work ??

Hi,

I’m having exactly the same problem where I need to display a custom post type under two different URLs based on which taxonomy they have selected from the navigation (clients/projects).

I’ve been looking for a while for a solution with many attempts involving modifying rewrite rules etc. to no avail.

How did you manage to solve it finally?