How to remove slug from CPT correctly?

Question

Im trying to remove slug from my Custom Post Types. I've added

'rewrite' => array(
    'slug' => '/'
)

and based on this post https://wordpress.stackexchange.com/a/144356/116847 I've added:

add_action( 'pre_get_posts', 'wpse_include_my_post_type_in_query' );
function wpse_include_my_post_type_in_query( $query ) {

     // Only noop the main query
     if ( ! $query->is_main_query() )
         return;

     // Only noop our very specific rewrite rule match
     if ( 2 != count( $query->query )
     || ! isset( $query->query['page'] ) )
          return;

      // Include my post type in the query
     if ( ! empty( $query->query['name'] ) )
          $query->set( 'post_type', array( 'post', 'page', 'physio_methods', 'treatment' ) );
 }

 add_action( 'parse_query', 'wpse_parse_query' );
function wpse_parse_query( $wp_query ) {

    if( get_page_by_path($wp_query->query_vars['name']) ) {
        $wp_query->is_single = false;
        $wp_query->is_page = true;
    }

}

otherwise, posts was mixed with pages and gets 404. But now, I have problem with posts categories - link to category display post, not the archive page.

I need to fully remove slug from my CPT. Is there any good (no plugin) solution for that?

Thanks!

Answer 1

This is a two-step process. First, you need to remove the slug from the default URL. (use a unique slug while registering the CPT).

function wpse413969_remove_cpt_slug( $post_link, $post ) {
    if ( $post->post_type == 'YOUR_CPT' && $post->post_status == 'publish') {
        $post_link = str_replace( '/' . $post->post_type . '/', '/', $post_link );
    }
    return $post_link;
}
add_filter( 'post_type_link', 'wpse413969_remove_cpt_slug', 10, 2 );

Then include your CPT in main query.

function wpse413969_add_cpt_names_to_main_query( $query ) {
   
    // Return if this is not the main query.
    if ( ! $query->is_main_query() ) {
        return;
    }
    
    // Return if this query doesn't match our very specific rewrite rule.
    if ( ! isset( $query->query['page'] ) || 2 !== count( $query->query ) ) {
        return;
    }
    
    // Return if we're not querying based on the post name.
    if ( empty( $query->query['name'] ) ) {
        return;
    }
    
    // Add CPT to the list of post types WP will include when it queries based on the post name.
    $query->set( 'post_type', array( 'post', 'page', 'YOUR_CPT' ) );
}
add_action( 'pre_get_posts', 'wpse413969_add_cpt_names_to_main_query' );

This, IMHO, is a bad practice. There are some good reasons why WordPress includes the slug in CPTs. To avoid conflict with default post and pages, always use unique slugs for your CPT posts.