Add Categories as CSS Classes

/***************************************************************************************
************************ [ ADD CATEGORIES AS CSS CLASSES ] ***************************/

function add_category_name($classes = '') {
   if(is_single()) {
      $category = get_the_category();
      $classes[] = 'category-'.$category[0]->slug;
   }
   return $classes;
}
add_filter('body_class','add_category_name');