List post wit the same category but exclude parent

Question

I have the followind code:

<?php global $post;
            $cat_ID=array();
            $categories = get_the_category(); //get all categories for this post
                foreach($categories as $category) {
                    array_push($cat_ID,$category->cat_ID);
                }
            $args = array(
                'orderby' => 'date',
                'order' => 'DESC',
                'post_type' => 'post',
                'numberposts' => 10,
                'post__not_in' => array($post->ID),
                'category__in' => $cat_ID
            );
            $cat_posts = get_posts($args);
                if ($cat_posts) {

                    echo 'SOME HTML';

                    foreach ($cat_posts as $cat_post) { ?>

It currently lists all post which contain the same category as the current post you are on. What I would like it to do is to exclude the parent category.

The a example category list / example would look like this:

Work
- Animation
- Film
- Misc

When on a post eith the cat Animation all the other posts with the same cat show up (which is good ) but so does the main parent 'Work'. How do I exclude it?

THANK YOU!

Answer 1

Top level categories will have value 0 for the parent, so check that before adding to the array:

foreach( $categories as $category ) {
    if( 0 != $category->parent ) {
        array_push( $cat_ID, $category->cat_ID );
    }
}