<?php
class CFunctions
{
    public function __construct ()
    {
        add_action('init', [$this, 'rewrite_rule_cpost']);
    }

    public function rewrite_rule_cpost()
    {
        $post_type = 'avada_portfolio';

        add_rewrite_tag( "%avada_portfolio%", '([^/]+)', "post_type=$post_type&name=" );
        $permastruct = "nefteprodukty/%avada_portfolio%"; // наша структура ЧПУ

        $args = array(
            'with_front'  => true,
            'paged'       => true,
            'ep_mask'     => EP_NONE,
            'feed'        => false,
            'forcomments' => false,
            'walk_dirs'   => false,
            'endpoints'   => false,
        );
        add_permastruct( $post_type, $permastruct, $args );
    }
}
new CFunctions();