usort is a PHP function with spooky behavior ?

As far as the php docs are concerned in the method The comparison function must return an integer less than, equal to, or greater than zero if the first argument is considered to be respectively less than, equal to, or greater than the second. But here is how I am using it with my posts

      foreach ($actualPosts as $post) {

            $post->sorter = [
                'sorter_date_time' => $post->created_at->diffForHumans(),
                'is_shared' => 'false',
                'post_sharer' => null
            ];

            
        }

In the above code I set the sorter_date_time to be string And then I use it inside usort

      usort($actualposts, function ($post1, $post2) {
            return $post2->sorter['sorter_date_time'] > $post1->sorter['sorter_date_time'];
        });

AND IT GIVES THE DESIRED RESULT!!.It gives the most recently created posts . How is this possible if I am using a string for comparison inside usort and not an integer?