Dropdown taxonomie lijst

function return_terms_index() {
  $taxonomies = array(
    'training_cat',
  );

  $args = array(
    'orderby'           => 'name',
    'order'             => 'ASC',
    'hide_empty'        => true,
    'fields'            => 'all',
    'parent'            => 0,
    'hierarchical'      => true,
    'child_of'          => 0,
    'pad_counts'        => false,
    'cache_domain'      => 'core'
  );

  $terms = get_terms($taxonomies, $args);

  $return .= '<ul class="trainingen">';

    foreach ( $terms as $term ) {

      // return terms (working)
      $return .= sprintf(
        '<li id="%1$s" class="checkbox"><a href="https://www.cls-trainingen.nl/opleidingen/?_training=%1$s">%2$s</a> <i class="xpnd fas fa-chevron-down"></i>',
        $term->slug,
        $term->name,
        $term->description
      );

        $subterms = get_terms($taxonomies, array(
          'parent'   => $term->term_id,
          'hide_empty' => true
          ));

        $return .= '<ul class="depth" style="display: none;">';

        foreach ( $subterms as $subterm ) {

          //return sub terms (not working :( )
          $return .= sprintf(
          '<li id="category-%1$s" class="link"><a href="https://www.cls-trainingen.nl/opleidingen/?_training=%1$s" class="sublink">%2$s</a> <span class="cat-description">%3$s</span>',
          $subterm->slug,
          $subterm->name,
          $subterm->description
          );

          $return .= '</li>'; //end subterms li
        }

        $return .= '</ul>'; //end subterms ul

      $return .= '</li>'; //end terms li
    } //end foreach term

  $return .= '</ul>';

return $return;
}

#dropdown #filter #functions #taxonomie #taxonomy