Then your PHP in the OP is what you want to put in. The version in post 12 will do the job.
PHP Code:
<?php
// categories_description
if ($current_categories_description != '') {
  
$php_content '';//build content to be substituted for PHP_SUB in description
  
if ($featured_products->RecordCount() > 0) {
    for (
$i 0$i $featured_products->RecordCount(); $i++) {
      
$php_content .= '<div class="categoryListBoxContents" style="width:33%;">';
      
$php_content .= '<a href="' zen_href_link(FILENAME_DEFAULT'main_page=product_info&products_id=' $featured_products->fields['products_id']) . '">';
      
$php_content .= zen_get_products_image($featured_products->fields['products_id']);
      
$php_content .= '</a></div>';     
    } 
  }
  
$current_categories_description str_replace('PHP_SUB'$php_content$current_categories_description);
?>
<div id="categoryDescription" class="catDescContent"><?php echo $current_categories_description;  ?></div>
<?php // categories_description ?>