Problem with widgets in Magento CMS?

Question

Magento

I am learning Magento, making a widget following the example of Creating a Magento Widget . I did everything according to the lesson, cleared the cache, the widget appeared in the list of widgets, I insert the widget on the page, I save it and nothing happens , the page is empty ...
I think ok, I probably messed up somewhere, well, well done from Magenta posted a link to the archive with the finished widget.
I copy the widget files to the server, clear the cache, click on the [Insert Widget] page and get:
Widget Insertion

Fatal error: Class 'Sample_WidgetOne_Helper_Data' not found in /home/lh/public_html/ms.com/app/Mage.php on line 523

The data.php file and the class in it are in place.
The question is, if you had such errors, where would you first look?
Thanks

Answer 1

I would look at the backtrace
the system cannot find the class,
check the paths, file names
and by the way the letter case Helpers/Data.php

Answer 2

If it doesn't find the class, then 1. it simply doesn't include the module. 2. wrong location or class name.