Register custom post types

add_action( 'init', function() {

	// Post Type
	$args = [
		'labels' => [ 'name' => 'Custom Items', 'singular_name' => 'Custom Item' ],
		'menu_icon' => 'dashicons-admin-site',
		'supports' => [ 'title', 'editor', 'thumbnail' ],
		'rewrite' => [ 'slug' => 'custom_item' ],
		'has_archive' => true,
		'show_in_menu' => true,
		'show_ui' => true,
		'publicly_queryable' => true,
		'exclude_from_search' => false,
		'hierarchical' => false,
		'can_export' => true,
		'show_in_nav_menus' => true,
		'query_var' => true,
		'show_in_rest' => false,
		'public' => true,
		'capability_type' => 'post',
	];
	register_post_type( 'custom_item', $args );

	// Post Type Category
	$args = [
		'labels' => [ 'name' => 'Custom Categories', 'singular_name' => 'Custom Category' ],
		'hierarchical' => true,
		'rewrite' => [ 'slug' => 'custom_category' ],
		'show_ui' => true,
		'show_in_nav_menus' => true,
		'show_tagcloud' => true,
		'show_admin_column' => false,
		'query_var' => true,
		'show_in_rest' => false,
	];
	register_taxonomy( 'custom_category', [ 'custom_item' ], $args );

} );