I need to get this sub nav to show up on cat, sup-cat and post

Question

This is some code that I have mixed together from around the web, what I am wanting it to do is show the sub-categories of what ever category it is in.

It seems to work on category, and sub-categories but wont show in the post its self.

<?php
if (is_category()) {
?>
<div id="bodywrap">
<div id="sub-nav" class="wrap">    
<?php    
$this_category = get_category($cat);
if($this_category->category_parent){
    $this_category = wp_list_categories('orderby=id&title_li=&child_of='.$this_category-        >category_parent."&echo=0");
}
else{
$this_category = wp_list_categories('orderby=id&title_li=&child_of='.$this_category-            >cat_ID."&echo=0");
}
if ($this_category) { 
    echo "<ul class=\"subnav\">". $this_category . "</ul>"; 
    echo "</div><div class=\"clearboth\"></div>";
}} 


else {
?>

<div id="sub-nav" class="wrap">
<h2 title="<?php bloginfo( 'description', 'display' ); ?>"><?php bloginfo( 'description' ); ?></h2>
</div>
<div class="clearboth"></div>
<div id="bodywrap">
<?php
}

?>

Answer 1

The reason it only works on category and sub-category pages is because is_category() checks to see if a Category archive page is being displayed. However a post is not an "archive page" it is a "single page" (see http://codex.wordpress.org/Template_Hierarchy). So you would need to add another condition in there that first checks to see if you are on a post page - using is_single() - and if so then retrieves the posts parent category and displays the sub-categories for that parent category.