Multiple Custom Post Types, Same URL Structure

Question

For some reason I can not create multiple CPT with the same URL structure, for instance I can not get the following to work:

/cpt1/overview
/cpt1/events

/cpt2/overview
/cpt2/events

What ends up happening is the following:

/cpt1/overview
/cpt1/events

/cpt2/overview-2
/cpt2/events-2

I tried the following on a clean install of wp to make sure nothing was messing it up:

add_action( 'init', function() 
{
    register_post_type( 'cpt1', array(
        'labels' => array(
            'name'                  => __('CPT1'),
            'singular_name'         => _x('Page', 'singular name'),
            'add_new'               => _x('Add New', 'page'),
            'all_items'             => __('All Pages'),
            'add_new_item'          => __('Add New Page'),
            'edit_item'             => __('Edit Page'),
            'new_item'              => __('New Page'),
            'view_item'             => __('View Page'),
            'search_items'          => _x('Search Pages', 'plural'),
            'not_found'             => _x('No pages found', 'plural'),
            'not_found_in_trash'    => _x('No pages found in Trash', 'plural'), 
            'parent_item_colon'     => '',
        ),
        'public' => true,
        'has_archive' => true,
        'rewrite' => array( 'slug' => 'cpt1', 'with_front' => false ),
        'show_in_nav_menus' => false,
        'hierarchical' => true,
        'supports' => array( 'author', 'title', 'editor', 'custom-fields', 'page-attributes', 'revisions' ),
    ));
} );

add_action( 'init', function() 
{
    register_post_type( 'cpt2', array(
        'labels' => array(
            'name'                  => __('CPT2'),
            'singular_name'         => _x('Page', 'singular name'),
            'add_new'               => _x('Add New', 'page'),
            'all_items'             => __('All Pages'),
            'add_new_item'          => __('Add New Page'),
            'edit_item'             => __('Edit Page'),
            'new_item'              => __('New Page'),
            'view_item'             => __('View Page'),
            'search_items'          => _x('Search Pages', 'plural'),
            'not_found'             => _x('No pages found', 'plural'),
            'not_found_in_trash'    => _x('No pages found in Trash', 'plural'), 
            'parent_item_colon'     => '',
        ),
        'public' => true,
        'has_archive' => true,
        'rewrite' => array( 'slug' => 'cpt2', 'with_front' => false ),
        'show_in_nav_menus' => false,
        'hierarchical' => true,
        'supports' => array( 'author', 'title', 'editor', 'custom-fields', 'page-attributes', 'revisions' ),
    ));
} );

Is what I am after possible? and how?

Further Discoveries

1

As I am working with this further .. it seems like wordpress will redirect the following (with out me doing any extra config) ...

/cpt2/overview/
/cpt2/events/

to

/cpt2/overview-2/
/cpt2/events-2/

2

I found the following wp function wp_unique_post_slug (with an available filter) which checks slugs for pages/posts returning a unique slug if it finds a duplicate (appending -2, -3, etc) .. if you look at the function itself, it does do a post_type check but only if the post_type is set as non hierarchical .. otherwise it finds all hierarchical post_types and checks for uniqueness from all (e.g. post, page, book, event .. as an example).

Answer 1

This is my solution to my problem above, I would love more feedback and/or a better solution ... the below uses code from wp_unique_post_slug which checks for slug uniqueness only within the custom post type and within the hierarchy.

Note: this works because cpt1 and cpt2 use their own permalink prefixes ...

add_filter( 'wp_unique_post_slug', function( $slug, $post_ID, $post_status, $post_type, $post_parent, $original_slug ) 
{
    if ( in_array( $post_type, array( 'cpt1', 'cpt2' ) ) )
    {
        // start with a base slug w/o any suffixes
        $slug = preg_replace( '/(-\d+)$/', '', $slug );

        global $wpdb, $wp_rewrite;

        $feeds = $wp_rewrite->feeds;
        if ( ! is_array( $feeds ) )
            $feeds = array();

        $check_sql = "SELECT post_name FROM $wpdb->posts WHERE post_name = %s AND post_type = %s AND ID != %d AND post_parent = %d LIMIT 1";

        $post_name_check = $wpdb->get_var( $wpdb->prepare( $check_sql, $slug, $post_type, $post_ID, $post_parent ) );

        if ( $post_name_check || in_array( $slug, $feeds ) || preg_match( "@^($wp_rewrite->pagination_base)?\d+$@", $slug )  || apply_filters( 'wp_unique_post_slug_is_bad_hierarchical_slug', false, $slug, $post_type, $post_parent ) ) {
            $suffix = 2;
            do {
                $alt_post_name = substr( $slug, 0, 200 - ( strlen( $suffix ) + 1 ) ) . "-$suffix";
                $post_name_check = $wpdb->get_var( $wpdb->prepare( $check_sql, $alt_post_name, $post_type, $post_ID, $post_parent ) );
                $suffix++;
            } while ( $post_name_check );
            $slug = $alt_post_name;
        }
    }

    return $slug;
}, 10, 6 );