Wordpress - Show all child categories associated to post ID within loop

Question

I'm looping through all posts and I'm trying to output the category nicename related to each post. So if there are categories A,B and C with post X only associated with categories A and C then I only want to output category A and C's nicename.

Here's the loop:

<?php $subs = new WP_Query( array( 'post_type' => 'case-study' ));
  if( $subs->have_posts() ) : while( $subs->have_posts() ) : $subs->the_post(); ?>

  <?php the_title(); ?>

  <p>Associated Child Categories</p>
  //Show nicenames of each child category associated to each post
  <?php $category = get_categories($post->ID);
        foreach(($category) as $cats) { echo $category->category_nicename; }?>

<?php endwhile; endif; ?>

Answer 1

It sounds like get_the_category() would be ideal for this situation, since you're doing this within The Loop:

$post_cats = get_the_category();
if ( $post_cats ) {
    foreach ( $post_cats as $cat ) {
        // Only show child categories (exclude parents)
        if ( ! $cat->category_parent === '0' ) {
            echo $cat->cat_name;
        }
    }
}