Display child category

Found this code to just display the child category but it only displays the child with category 8. How can I display the child categories of all parent categories? Tried adding the others like 8,10,11,12 but that doesn’t work?

<?php the_title_attribute(); ?>"><?php the_title(); ?></a></td>
<td align="center"><?php
foreach((get_the_category()) as $childcat) {
if (cat_is_ancestor_of(8, $childcat)) {
echo '<a href="'.get_category_link($childcat->cat_ID).'">';
echo $childcat->cat_name . '</a>';
}}
?>

Thanks