WordPress.org

what you didn't like with the ealier attempt comes from wordpress' way of naming the slugs of categories if the category names appear double as subcategories of different parents;
this new code uses the category names and turns them into a sanitized form, so the names are lowercase with hyphens (instead of spaces - similar to slugs)

<?php $cats = get_the_category($post->ID);
$subcategories = array();
foreach( $cats as $cat ) {
  $subcats = get_categories('child_of='.$cat->term_id);
  if($subcats) {
    foreach( $subcats as $subcat )
      {  $subcategories[] = sanitize_title($subcat->name); }
  }
}
$subcats = array_unique($subcategories);
if($subcats) {
  $subcats = implode(' ',$subcats);
  echo 'class="' . $subcats . '"';
}
?>

Appreciate taking your time to help me out. Thanks

When I run the code, it gives me all the sub-categories inside of the main category. I'm just trying to find the sub-categories that are selected for each post in the loop...

...
<?php query_posts('cat=14&showposts=3'); ?>
<?php $posts = get_posts('category=14&numberposts=3&offset=0');  ?>
<?php foreach ($posts as $post) : start_wp(); ?>

<?php $cats = get_the_category($post->ID);
    $subcategories = array();
    foreach( $cats as $cat ) {
    $subcats = get_categories('child_of='.$cat->term_id);
    if($subcats) {
    foreach( $subcats as $subcat )
      {  $subcategories[] = sanitize_title($subcat->name); }
    }
    }
    $subcats = array_unique($subcategories);
    if($subcats) {
    $subcats = implode(' ',$subcats);
    echo '<li class="' . $subcats . '">';
    }
    ?>
.......

<?php endforeach ?>
...

If a blog post is in the main category of "Projects" and has 2/4 sub-categories, display the 2 sub-categories.

i think i'm getting it now:

you only want to show the category name of the post's category which is also at sub-category level - as a css class in the li tag that surrounds your post.

last try, in the context of your code:

<?php $posts = get_posts('category=14&numberposts=3&offset=0');  ?>
<ul>
<?php foreach ($posts as $post) : start_wp(); ?>
<li <?php $cats = get_the_category($post->ID);
$subcats = array();
foreach( $cats as $cat ) {
  $cat = get_category($cat->term_id);
  if($cat->parent) { $subcats[] = sanitize_title($cat->name); }
}
 if($subcats) { echo 'class="';
 foreach($subcats as $subcat) { echo $subcat . ' '; }
 echo '"';
}?>>
.......
</li>
<?php endforeach ?>
</ul>
...

YES!

Brilliant, thanks a lot alchymyth.

Cheers,
Simon

you're welcome.

'third time lucky' ;-)