Display List of Categories Within a Custom Taxonomy

Question

My website is an online magazine, so I have a custom function that creates a taxonomy (Volume/Issue) for Posts and Pages.

Each issue of the magazine has its own particular category (e.g. News, Alumni, Web Extras).

How do I get WordPress to programmatically display the appropriate populated categories for each Volume/Issue taxonomy?

For instance, in Issue v12n1, display a link to the News & Alumni archive page. In Issue v11n1, do the same for News & Web Extras (assuming there is no Alumni in v11n1 nor Web Extras in v12n1).

Is this even possible?

I've tried the get_terms function, but I'm too limited as I'm only calling one category's parent, not the applicable taxonomy:

$volume = get_the_volume($post); //the custom function
$departments = get_terms('category', array(
              'orderby'     => 'ID',
              'post_type' => 'post',
              'volume' => $volume,
              'category__not_in' => array(2, 9),
              'order'     => 'ASC',
              'hide_empty'  => true,
              'parent'      => '81',
              ));

        if ( ! empty( $departments ) && ! is_wp_error( $departments ) ) {
                $count = count( $departments );
                $i = 0;
                $department_list = '';
                foreach ( $departments as $department ) {
                    $i++;
                  $department_list .= '<li><a href="' . get_term_link( $department ) . '" title="' . sprintf( __( 'View all post filed under %s', 'my_localization_domain' ), $department->name ) . '">' . $department->name . '</a></li>';
                }
                echo $department_list;
            } ?>

Answer 1

It's hard to understand how you use your taxonomy and where you want to display it.

Does your posts have a custom taxonomy and you want to display it there? Or you have some page, like /issues/, with a list of posts that linked to a certain issue number and grouped some how?

So, if you want to retrieve a categories based on custom taxonomy, you could use this code:

In your functions.php define this function:

function my_custom_function() {
    global $post;
    $result = get_the_term_list( $post->ID, 'people', '<span>', '&nbsp;', '</span>');
    echo $result;
}

Then in your loop inside a theme files just call it.

single-something.php

<?php my_custom_function(); ?>

It's important to understand, that we don't know your implementation details, and you should provide a Post Id by yourself. Through, it's a working, tested example which retrieves every category for a given post.

And I think you would be easier to just retrieve categories.