/**
 * Add support for Field Group categories to Advanced Custom Fields (WordPress plugin).
 *
 * Drop this code into your theme's functions.php or equivalent file. This will
 * then allow you to add categories to Field Groups on the edit screen. It also
 * adds a "Category" column to the Field Groups list page - users can click
 * on the category name to filter the Field Groups by that category.
 *
 * @author Stefan Crowe <me@stefancrowe.co.uk>
 */

/**
 * Register ACF Field Group category
 */
function register_acf_field_category()
{
    $args = array(
        'hierarchical'               => true,
        'public'                     => false,
        'show_ui'                    => true,
        'show_in_nav_menus'          => true,
    );

    register_taxonomy( 'acf-field-category', array( 'acf-field-group' ), $args );
}

add_action('init', 'register_acf_field_category', 0);

function acf_field_group_columns($columns)
{
    $columns['acf-field-category'] = __('Category');

    return $columns;
} // end function reference_columns

add_filter('manage_edit-acf-field-group_columns', 'acf_field_group_columns', 20);

function acf_field_group_columns_content($column, $post_id)
{
    switch ($column) {
        case 'acf-field-category':
            global $post;
            $terms = get_the_terms($post->ID, 'acf-field-category');

            if ($terms) {
                $term = array_pop($terms);

                echo '<a href="?post_type=acf-field-group&acf-field-category=' . $term->slug . '">' . $term->name . '</a>';
            } else {
                echo '-';
            }

            break;
        default:
            break;
    } // end switch
} // end function reference_columns_content
add_action('manage_acf-field-group_posts_custom_column', 'acf_field_group_columns_content', 20, 2);