List one post only from each subcategory using get_posts?

Question

Custom Post Type = 'projects' with a Hierarchical Taxonomy = 'projects_category'

projects
- big-corporates
-- company one
---- first project 1
---- second project 1
---- third project 1
-- company two
---- first project 2
---- second project 2
-- company three
---- first project 3
---- second project 3
---- third project 3
- small-businesses
-- company four
---- first project 4
---- etc...
-- company five
-- company six

Below I get a list of all projects listed in 'projects_category' under 'big-corporates' whereas I want to limit the list to just one project from each subcategory of 'big-corporates'.

<?php
    global $post;
    $args = array( 'post_type' => 'projects', 'projects_category' => 'big-corporates' );
    $myposts = get_posts( $args );
    foreach( $myposts as $post ) :  setup_postdata($post); ?>
        <li><a href="<?php the_permalink(); ?>" title="<?php the_title_attribute(); ?>"><?php #the_title(); ?><?php $terms = get_the_term_list( $post->ID, 'projects_category' ); $terms = strip_tags( $terms ); echo $terms; ?></a></li>
    <?php endforeach; ?>

I am trying to achieve a list like this:

company one (links to first project 1)
company two (links to first project 2)
company three (links to first project 3)

How can I do that?

Answer 1

I'm not sure this is the best way but it works:

//First get all child categories if 'big_corporates'
$categories = $args = array(
    'parent'                   => $big_corporates_ID,
    'orderby'                  => 'name',
    'order'                    => 'ASC',
    'hide_empty'               => 1,
    'taxonomy'                 => 'projects_category'
    );

//then loop over them and get the first post of each:
echo '<ul>';
foreach ($categories as $category) {
    $projects = get_posts(array('numberposts' => 1, 'post_type' => 'projects', 'projects_category' => $category->slug));
    foreach( $projects as $project ) {
        setup_postdata($project);
        ?><li><?php echo $category->name; ?> - <a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></li><?php
    }
}
echo '</ul>';