Can this be a widget

Hello,

I try to make this a widget: https://floatleft.com/notebook/wordpress-year-month-archives/

I use this tutorial for it : https://www.wpexplorer.com/create-widget-plugin-wordpress/

But still I see a lot of errormessages like this one :
Parse error: syntax error, unexpected ‘<‘ in /home/vhosting/c/vhost0008707/domains/tamarawobben.nl/htdocs/test/wp-content/plugins/custom_archive/archive_custom.php on line 60

So I wonder if my idea can work and if someone is willing me to make it work.

Roelof