Add default taxonomies to a custom post type

In WordPress, the basic taxonomies, categories and tags, are only set up to be used on the default post type. If you want to add them to a custom post type you’ve created, you can do so by adding category and/or post_tag to the taxonomies array element in the post type’s argument array.

Full example

<?php

// Register Movie Post Type

function register_movie_post_type()
{
  $labels = array(
    'name' => __('Movies', 'movie'),
    'singular_name' => __('Movie', 'movie'),
    'add_new' => __('New Movie', 'movie'),
    'add_new_item' => __('Add New Movie', 'movie'),
    'edit_item' => __('Edit Movie', 'movie'),
    'new_item' => __('New Movie', 'movie'),
    'view_item' => __('View Movie', 'movie'),
    'search_items' => __('Search Movies', 'movie'),
    'not_found' =>  __('No Movies Found', 'movie'),
    'not_found_in_trash' => __('No Movies found in Trash', 'movie'),
  );

  $args = array(
    'labels' => $labels,
    'public' => true,
    'publicly_queryable' => true,
    'hierarchical' => false,
    'supports' => array(
      'title',
      'editor',
      'author',
      'excerpt',
      'custom-fields',
      'thumbnail',
      'revisions',
    ),
    'taxonomies' => array('category', 'post_tag'),
    'rewrite' => array('slug' => 'movie'),
    'show_in_rest' => true,
    'menu_icon' => 'dashicons-video-alt3',
  );

  register_post_type('movie', $args);
}

add_action('init', 'register_movie_post_type', 5);