【WordPress】投稿画面に既存タグを一覧で表示する方法

/**
 * 投稿画面にタグ一覧を表示しチェックボックス選択式にする
 */
function re_register_post_tag_taxonomy() {
  $tag_slug_args = get_taxonomy('post_tag');
  $tag_slug_args->hierarchical = true;
  $tag_slug_args->meta_box_cb = 'post_categories_meta_box';
  register_taxonomy('post_tag', 'post', (array) $tag_slug_args);
}
add_action( 'init', 're_register_post_tag_taxonomy', 1 );

function re_register_post_tag_taxonomy() {
global $wp_rewrite;
$rewrite = array(
'slug' => get_option('tag_base') ? get_option('tag_base') : 'tag',
'with_front' => ! get_option('tag_base') || $wp_rewrite->using_index_permalinks(),
'ep_mask' => EP_TAGS,
);
 
$labels = array(
'name' => _x( 'Tags', 'taxonomy general name' ),
'singular_name' => _x( 'Tag', 'taxonomy singular name' ),
'search_items' => __( 'Search Tags' ),
'popular_items' => __( 'Popular Tags' ),
'all_items' => __( 'All Tags' ),
'parent_item' => null,
'parent_item_colon' => null,
'edit_item' => __( 'Edit Tag' ),
'view_item' => __( 'View Tag' ),
'update_item' => __( 'Update Tag' ),
'add_new_item' => __( 'Add New Tag' ),
'new_item_name' => __( 'New Tag Name' ),
'separate_items_with_commas' => __( 'Separate tags with commas' ),
'add_or_remove_items' => __( 'Add or remove tags' ),
'choose_from_most_used' => __( 'Choose from the most used tags' ),
'not_found' => __( 'No tags found.' )
);
 
register_taxonomy( 'post_tag', 'post', array(
'hierarchical' => true,
'query_var' => 'tag',
'rewrite' => $rewrite,
'public' => true,
'show_ui' => true,
'show_admin_column' => true,
'_builtin' => true,
'labels' => $labels
) );
}
add_action( 'init', 're_register_post_tag_taxonomy', 1 );