如何在wordpress中按类别名称获取子类别？

Question

我想通过父类别名称获取所有子类别，这是我当前的代码

<?php
//get all categories then display all posts in each term
$taxonomy = 'category';
$param_type = 'category__in';
$term_args=array(
  'orderby' => 'name',
  'order' => 'ASC',
);

$terms = get_terms($taxonomy,$term_args);
if ($terms) {
  foreach( $terms as $term ) {
    $args=array(

      "$param_type" => array($term->term_id),

      'post_type' => 'portfolio',
      'category_name'    => 'web-design',
      'order' => 'ASC',
      'post_status' => 'publish',
      'posts_per_page' => 6,
      'caller_get_posts'=> 1
      );
    $my_query = null;

    $my_query = new WP_Query($args);
    if( $my_query->have_posts() ) {  ?>

正如您所看到的，我使用投资组合作为自定义帖子类型和网页设计作为父类别名称，我想获得父类别的所有子类别，即web-design