Simple Code (NEED IT!): Get Sub-Categories While on Post Page

Hi,
I use this code for single page with. Explanation is maybe a little big long, but it may help.

TERMS USED
category = any category
parent category = category with subcategories
child category = child (subcategory) of parent category

REMARKS
every category has parent category ID -> if category has no parent, parent ID = 0

PROCEDURE
1. get current post parent category ID
2. check parent category ID -> if is 0, it is category without children
3. get subcategories
4. check which of subcategories is current and add current-cat div to it
5. format data for output
6. echo subcategory list

FUNCTIONS
get_the_category () and get_category () returns stdClass Object for one, or array of stdClass Objects for many post categories and subcategories, depedens on ($args)

category stdClass Object contains next category objects
[term_id] => category ID
[name] => category name
[slug] => category slug
…
[description] => category description
…
[count] => No of posts in category
…
[category_parent] => parent category ID; if category is parent, ID = 0

VARIABLES
$postcat -> current post categories IDs
$cat -> post first category ID
$thiscat -> post first category objects
$parent -> post first category parent ID

<?php

	//* first let's get current post parent category ID

	$ID = $wp_query->posts[0]->ID; //* get current post ID
	$postcat = get_the_category($ID); //* based on post ID, get current post categories IDs -> WP function returns array of stdClass Objects, one stdClass Object for each category; if there is child - parent relationship, first it will return Objects for children categories and than for parents -> add "print_r ($postcat);" without quotation marks in next row to see content of array
	$cat = $postcat[0]->cat_ID; //* get first category ID from first Object in $postcat array (if post has children categories, it will get first child ID, else it will get first category ID)
	$thiscat = get_category ($cat); //* get array of category objects for $cat (current) category -> add "print_r ($thiscat);" without quotation marks in next row to see content of array
	$parent = $thiscat->category_parent; //* and extract parent category ID; if category has no parent category (and parent category has no parent), ID = 0

	//* now we have current category parent ID No, or if category has no children ID = 0
	//* let's check if we heave categroy with children categories or not

	if ($parent == 0) //* if parent ID = 0, it is category without chlidren

		{} //* do nothing 

	else { //* else, if it has children categories

		$subcategories = get_categories('child_of='.$parent); //* get array of children categories Objects and

		//* this next part is Marks (t31os) code from WP forum topic 'Showing subcategories of a parent page under subcategory'

		$items=''; //* create new ArrayObject and

			foreach($subcategories as $subcat) { //* foreach child category in array
				if($thiscat->term_id == $subcat->term_id) //* check if current category ID is same as child category ID
				$current = ' current-cat'; //* if true, add current-cat to li class
				else $current = ''; //* if not, add nothing

				$items .= '
				<li class="cat-item cat-item-'.$subcat->term_id.$current.'"> <!-- if is child current, add here .current-cat //-->
					<a href="'.get_category_link( $subcat->term_id ).'" title="'.$subcat->description.'">'.$subcat->name.' ('.$subcat->count.' posts)</a> <!-- link to -> category link, title -> category description, show -> category name and No of posts //-->
				</li>';
			}

		echo "<ul>$items</ul>";
	}
?>