Multiple permalinks for a single post with multiple taxonomies

Question

I created 1 custom post type (projects) with 2 taxonomies (clients / fields) to filter the results (like categories).

At the end, it should be like this where project_name is the same custom post displayed in single-projects.php :

• my-site/projects/
• my-site/projects/project_name
• my-site/projects/fields/
• my-site/projects/fields/project_name
• my-site/projects/clients/
• my-site/projects/clients/project_name

Like this, based on the re-written url, i'll be able to easily display the current term selected and navigate post per post (in single-projects.php) within this specific term .

I'm using an archive to display all custom posts: archive-projects.php.

The custom posts permalinks are like this: my-site/projects/project_name

I've got a taxonomy template to display custom posts related to a term and it's working well: taxonomy.php

So far so good.

But permalinks are still like this : my-site/projects/project_name.

And i'd like to give them a different permalink based on the current taxonomy and get a different URL as written above.

I already found this and it's working well in a standard case (a blog with few categories for example), but i got stuck when i'm trying to adapt to taxonomies. I can create the new url but can't give it to the permalink post.

Any help or advice? thanks

[UPDATE] Here is what i managed to do so far :

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'))
{
  $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');

it displays well the new permalinks on taxonomy template and redirections are pointing to the desired post but WP keeps writing the single post url as my-site/projects/project_name. Is it because the targeted post is a custom post type ?

Answer 1

I'm about to release a plugin to do just that (and some other things). You'll have to modify your rewrite rules. This code works for category posts. Perhaps, if you work on it a little bit it will get you the same behavior for post types and taxonomies.

First, generate the rules you need:

function get_category_rules() {
    $rules = array();

    /*
    * Will generate patterns for:
    *  (category)/
    *  category/(subcategory)
    *  category/subcategory/(post)
    *  feed/(category)
    *  feed/category/(subcategory)
    */

    $feed_sufix = '/feed/?(rss|rss2|atom)?/?$';
    $page_sufix = '/page/?([0-9]{1,})?/?$';

    /* Walk within the categories by level */

    $categories = get_categories(array(
        'orderby'    => 'slug',
        'hide_empty' => false,
        'exclude'    => implode(',', $excludes)
    ));
    foreach($categories as $category) {

        $level = 0;
        $path = '(' . $category->slug . ')';

        while (($category = get_category($category->parent)) && isset($category->term_id)) {
            $level++;
            $path = $category->slug . '/' . $path;
        }

        // Feeds
        $rules[$level][$path . $feed_sufix] = 'index.php?category_name=$matches[1]&feed=atom';

        // Category archives
        $rules[$level][$path . '/?$'] = 'index.php?category_name=$matches[1]';

        // Category archive pages
        $rules[$level][$path . $page_sufix] = 'index.php?category_name=$matches[1]&paged=$matches[2]';

        // Posts
        $rules[$level][$path . '/([^/]+)/?$'] = 'index.php?name=$matches[2]';

    }

    $retval = array();
    for ($i = count($rules) - 1; $i >= 0; $i--) {
        $retval = array_merge($retval, $rules[$i]);
    }
    return $retval;
}

Then, merge these rules with the existing ones:

add_action('rewrite_rules_array', 'rewrite_rules');
function rewrite_rules($rules) {
    $category_rules = get_category_rules();
    $rules = array_merge($category_rules, $rules);
    return $rules;
}

And make *_permalink functions work with it.

add_filter('post_link', 'custom_post_permalink');
function custom_post_permalink ($post_link) {
    global $post;

    $cats = array_reverse(get_the_category($post->ID));
    if (!isset($cats[0]))
        return $post_link;

    $category = $cats[0];
    $path = $category->slug;

    while (($category = get_category($category->parent)) && isset($category->term_id)) {
        $path = $category->slug . '/' . $path;
    }

    return str_replace(home_url(), home_url() . '/' . $path, $post_link);
}