Wordpress - Ability to get category and all sub-categories

CategoryOrSub

/*
Snippet Name: Category or Subcategory
Description: Gets the category and all subcategories of a cat_ID
Usage: Ideal if you are trying to put code only on the categories of a cat and it's children, in lieu of doing an array of all the children. Put the following code in functions.php or a plugin.
*/
<?php if (!function_exists('is_category_or_sub')) {
  function is_category_or_sub($cat_id = 0) {
    foreach (get_the_category() as $cat) {
      if ($cat_id == $cat->cat_ID || cat_is_ancestor_of($cat_id, $cat)) 
        return true;
    }
    return false;
  }
} ?>
/* 
example: To add code to category 1 and it's children
<?php if(is_category_or_sub(1)) {
  //put code here
} ?>
*/