WordPress: Get Categories sorted by modified posts

So, I had a project in WordPress where I have to display all categories of the page sorted by the last update of a post which belongs to a category.

For example: Category A consists of one post created yesterday; Category B consists of one post created today

In this case B is before A. But if I edit the post of A, category A will be before B.

I tried a lot of stuff in the web which should do this, but it doesn't work, so I write an own function.

Steps:

1. First put the code located in code.php in your functions.php of your theme
2. Then call the function netthemes_sorted_categories() in your template. So you can do something like this:

$categories = netthemes_sorted_categories();
foreach ( $categories as $category ) {
   echo $category->name;
}

This will display all category names sorted by its modified posts.

Hint:

In line 35 of the code.php you also display all categories which doesn't have posts. If you don't want to display them, just remove this part:

//Get all empty categories
$args_cat = array(
  'parent' => 0,
  'hide_empty' => FALSE,
  'orderby' => 'name'
);
$categories = get_categories( $args_cat );
foreach($categories as $category) {
   if($category->count == 0) {
      array_push($catarr, $category);
   }
}

If you've question or discover some issues, comment in the issue section.