Give specific category its own permalink structure

Question

For the purposes of my site, I have my Permalinks set to /blog/%postname%/ for all posts.

However, I need to give Posts with a specific Category (in this case, "Testimonials") its own permalink structure, where each individual post assigned the Category "Testimonials" returns as /testimonials/%postname%/ and the Category Archive page returns as /testimonials/.

Here is the code I have so far:

//Rewrite URLs for "testimonial" category
add_filter( 'post_link', 'custom_permalink', 10, 3 );
function custom_permalink( $permalink, $post, $leavename ) {
    // Get the category for the post
    $category = get_the_category($post->ID);
    if (  !empty($category) && $category[0]->cat_name == "Testimonials" ) {
        $cat_name = strtolower($category[0]->cat_name);
        $permalink = trailingslashit( home_url('/'. $cat_name . '/' . $post->post_name .'/' ) );
    }
    return $permalink;
}

add_action( 'init', 'custom_rewrite_rules' );
function custom_rewrite_rules() {
    add_rewrite_rule(
        'testimonials/([^/]+)(?:/([0-9]+))?/?$',
        'index.php?category_name=testimonials&name=$matches[1]&page=$matches[2]',
        'top' // The rule position; either 'top' or 'bottom' (default).
    );
}

This successfully returns each individual post with the category "Testimonials" as /testimonials/%postname%/. However, the Category Archive page returns as /blog/category/testimonials. I need this to just return as /testimonials/, while still returning all other Posts as /blog/%postname%/

I tried using this plugin, https://wordpress.org/plugins/custom-permalinks/, which solved the Category Archive page issue, but broke each individual testimonial post, returning them as a 404 error.

In this case, I cannot register Testimonials as a Custom Post Type as it will affect other site functionality,

Answer 1

Try these steps:

Step #1: Replace this:

add_action( 'init', 'custom_rewrite_rules' );
function custom_rewrite_rules() {
    add_rewrite_rule(
        'testimonials/([^/]+)(?:/([0-9]+))?/?$',
        'index.php?category_name=testimonials&name=$matches[1]&page=$matches[2]',
        'top' // The rule position; either 'top' or 'bottom' (default).
    );
}

..with this one:

add_filter( 'category_link', 'custom_category_permalink', 10, 2 );
function custom_category_permalink( $link, $cat_id ) {
    $slug = get_term_field( 'slug', $cat_id, 'category' );
    if ( ! is_wp_error( $slug ) && 'testimonials' === $slug ) {
        $link = home_url( user_trailingslashit( '/testimonials/', 'category' ) );
    }
    return $link;
}

add_action( 'init', 'custom_rewrite_rules' );
function custom_rewrite_rules() {
    add_rewrite_rule(
        'testimonials(?:/page/?([0-9]{1,})|)/?$',
        'index.php?category_name=testimonials&paged=$matches[1]',
        'top' // The rule position; either 'top' or 'bottom' (default).
    );

    add_rewrite_rule(
        'testimonials/([^/]+)(?:/([0-9]+))?/?$',
        'index.php?category_name=testimonials&name=$matches[1]&page=$matches[2]',
        'top' // The rule position; either 'top' or 'bottom' (default).
    );
}

Step #2: Go to the Permalink Settings page, and click on the Save Changes button without actually making any changes.

Answer 2

Why not just add the post id then? If that's all you need? You could just do this with query_vars

add_filter('query_vars', 'my_query_vars' );

You only need to check if you are in the 'special' category and if yes, add the var. Then utilizing the pre_get_posts hook, check if your post contains an ID and if yes change your query to get desired post.