New Post type and Taxonomy WP

NewPostType.php

<?php

class NewPostType
{
    const LABEL = 'label';
    const LABELS = 'labels';
    const VALUE = 'value';
    const DESCRIPTION = 'description';
    const TYPE = 'type';
    const BACK_DOMAIN = 'art-fields';

    const POST_TYPE = 'art-gallery';
    const TAX_TYPE = 'case';

    public function init()
    {
        add_action('init', [$this, 'registerPostType'], 0);
        add_action('init', [$this, 'createGalleryTax'], 0);
        add_action('init', [$this, 'registerTaxonomy'], 0);

        add_action('init', [$this, 'post_for_taxonomy'], 0);

        add_action('post_type_link', [$this, 'galleryPermalink'], 10, 2);
        add_filter('post_updated_messages', [$this, 'true_post_type_messages']);

//        add_action('init', [$this, 'unregister']);
    }

    public function registerPostType ()
    {
        $labels = array(
            'name' => __('Gallery', 'art-fields'),
            'singular_name' => __('Gallery item', 'art-fields'),
            'add_new' => __('Add Gallery', 'art-fields'),
            'add_new_item' => __('Add new item', 'art-fields'),
            'edit_item' => __('Edit item', 'art-fields'),
            'new_item' => __('New item', 'art-fields'),
            'all_items' => __('Galleries', 'art-fields'),
            'view_item' => __('View item', 'art-fields'),
            'search_items' => __('Search item', 'art-fields'),
            'not_found' =>  __('Not found', 'art-fields'),
            'not_found_in_trash' => __('There are no items in the cart', 'art-fields'),
            'menu_name' => __('Gallery', 'art-fields'),
            'menu_icon' => 'dashicons-admin-customizer',
        );

        register_post_type(self::POST_TYPE, array(
            self::LABEL => __('Gallery', self::BACK_DOMAIN),
            self::DESCRIPTION=> __('All lots from all galleries', self::BACK_DOMAIN),
            self::LABELS => $labels,
            'supports' => array('title', 'editor', 'thumbnail', 'custom-fields',),
            'taxonomies' => array(self::TAX_TYPE),
            'public' => true,
            'show_ui' => true,
            'show_in_menu' => true,
            'show_in_nav_menus' => true,
            'show_in_admin_bar' => true,
            'menu_position' => 5,
            'can_export' => true,
            'hierarchical' => false,
            'rewrite' => array(
                'slug' => 'gallery/%' . self::TAX_TYPE . '%',
                'with_front' => false,
                'pages' => false,
                'feeds' => false,
                'feed' => false
            ),
            'has_archive' => true,
            'query_var' => true,
            'exclude_from_search' => false,
            'publicly_queryable' => true,
            'capability_type' => 'post',
        ));
    }

    public function registerTaxonomy(){
        register_taxonomy_for_object_type( self::TAX_TYPE, self::POST_TYPE);
    }

    function createGalleryTax() {
        register_taxonomy(
            self::TAX_TYPE,
            self::POST_TYPE,
            array(
                self::LABELS => array(
                    'name' => _x('Case', self::BACK_DOMAIN),
                    'menu_name' => __('Cases', self::BACK_DOMAIN),
                    'singular_name' => _x('Case', self::BACK_DOMAIN),
                    'search_items' => __('Search Case', self::BACK_DOMAIN),
                    'popular_items' => __('Popular Case', self::BACK_DOMAIN),
                    'all_items' => __('All Case', self::BACK_DOMAIN),
                    'parent_item' => __('Parent Case', self::BACK_DOMAIN),
                    'parent_item_colon' => __('Parent Case', self::BACK_DOMAIN),
                    'edit_item' => __('Edit Case', self::BACK_DOMAIN),
                    'update_item' => __('Update Case', self::BACK_DOMAIN),
                    'add_new_item' => __('Add New Case', self::BACK_DOMAIN),
                    'new_item_name' => __('New Case Number', self::BACK_DOMAIN),
                    'separate_items_with_commas' => __('Separate case with commas', self::BACK_DOMAIN),
                    'add_or_remove_items' => __('Add or remove cases', self::BACK_DOMAIN),
                    'choose_from_most_used' => __('Choose from the most used cases', self::BACK_DOMAIN),
                ),
                'rewrite' => array(
                    'slug' => 'gallery',
                    'with_front' => true,
                    'pages' => false,
                    'feeds' => false,
                    'feed' => false,
                ),
                'public' => true,
                'show_in_nav_menus' => false,
                'show_ui' => true,
                'show_tagcloud' => false,
                'update_count_callback' => '_update_post_term_count',
                'hierarchical' => true,
                'show_admin_column' => true,
                'query_var' => true,
            )
        );
    }

    public function post_for_taxonomy()
    {
        register_taxonomy_for_object_type(self::TAX_TYPE, self::POST_TYPE);
    }

    public function true_post_type_messages( $messages ) {
        global $post, $post_ID;

        $messages[self::POST_TYPE] = array(
            0 => '',
            1 => sprintf( 'Gallery update. <a href="%s">View</a>', esc_url( get_permalink($post_ID) ) ),
            2 => 'Parameter update',
            3 => 'Parameter removed',
            4 => 'Item update',
            5 => isset($_GET['revision']) ? sprintf( 'Item restored from revision: %s', wp_post_revision_title( (int)
            $_GET['revision'], false ) ) : false,
            6 => sprintf( 'Item published on the site. <a href="%s">View</a>', esc_url( get_permalink($post_ID)
            ) ),
            7 => 'Function saved.',
            8 => sprintf( 'Submitted for review. <a target="_blank" href="%s">View</a>', esc_url( add_query_arg( 'preview', 'true', get_permalink($post_ID) ) ) ),
            9 => sprintf( 'Scheduled for publication: <strong>%1$s</strong>. <a target="_blank" href="%2$s">View</a>',
                date_i18n( __( 'M j, Y @ G:i' ), strtotime( $post->post_date ) ), esc_url( get_permalink($post_ID) ) ),
            10 => sprintf( 'Draft updated. <a target="_blank" href="%s">View</a>', esc_url( add_query_arg( 'preview',
                'true', get_permalink($post_ID) ) ) ),
        );

        return $messages;
    }

    public function galleryPermalink($permalink, $post) {
        if (strpos($permalink, '%' . self::TAX_TYPE . '%') === false) {
            return $permalink;
        }

        $terms = get_the_terms($post, self::TAX_TYPE);
        if (!is_wp_error($terms) && !empty($terms) && is_object($terms[0])) {
            $term_slug = array_pop($terms)->slug;
        } else {
            $term_slug = 'gallery';
        }

        return str_replace('%' . self::TAX_TYPE . '%', $term_slug, $permalink);
    }

    public function unregister()
    {
        unregister_post_type(self::POST_TYPE);
        unregister_taxonomy(self::TAX_TYPE);
    }
}
(new NewPostType())->init();