Display Only Child Category in WordPress Post Loop

To display only Child Category in the post loop (mostly single.php), all you have to do is replace the following code:

1	<?php the_category(', '); ?>

with this code:

1 2 3 4 5 6 7

<?php foreach((get_the_category()) as $childcat) { if (cat_is_ancestor_of(9, $childcat)) { echo '<a href="'.get_category_link($childcat->cat_ID).'">';  echo $childcat->cat_name . '</a>'; }} ?>

Remember to change the number 9 to your parent category’s ID.