How to display the names of subcategories of a certain category, Wordpress?

Question

PHP

Good evening!
Made a portfolio with filtering based on this article.

<div class="container content">
    <div class="row row-margin">
      <?php $args = array(
        'parent'                   => 15,
        'hide_empty'               => 1,
        'number'                   => '0',
        'taxonomy'                 => 'category',
        'pad_counts'               => true );
         
        $catlist = get_categories($args);
      ?>
      <ul id="filters" class="clearfix">
        <li><span class="filter active" data-filter="portrait wedding">all</span></li>
        <?php
          foreach ($catlist as $categories_item) {
            echo "<li><span class=\"filter\" data-filter=\"$categories_item->cat_name\">" . $categories_item->cat_name . "</li>";
          }
        ?>
      </ul>
      <div id="portfoliolist">
        
        <?php 
          $query = new WP_Query( array( 
          'post_type' => 'post', 
          'posts_per_page' => -1,
          ) ); 
        ?>
        <?php 
          while ($query->have_posts()) : 
          $query->the_post();
        ?>
          <?php $category = get_the_category(); ?>
          <div class="col-lg-3 col-md-4 col-sm-6 col-xm-12 portfolio <?php echo $category[0]->cat_name; ?>" data-cat="<?php echo $category[0]->cat_name; ?>">
            <div class="block-active">
              <?php the_post_thumbnail('thumbnail'); ?>
            </div><!--/block-active-->
          </div><!--/col-->
        <?php endwhile; ?>
      </div><!--portfoliolist-->		
    </div><!--/row-->
  </div><!--/container-->

But to make it even more logical, I thought to filter based on subcategories. That is, there will be one category "Portfolio", from which all posts will be displayed, and filtering will already be by subcategories. But so far I have not succeeded. Someone can help?

Answer 1

It is more logical to make a custom post type "Portfolio", for it the taxonomy "Portfolio Categories" and display / filter by these categories.