Two or more instances of this results in multiple ids #subbox

I want to use this plugin in my footer and in a sidebar or in a widget area below the post content, but when there are more than one on the page, there are duplicate ids which is an error. I corrected this by adding:

-<?php echo $this->id; ?>

To each string subbox, subbox1, subbox2, subbutton in various locations. I am assuming that you added this for accessibility between the label and the field, so this should work to accomplish that and be a unique id for each instance, just like the widget itself.

Let me know if you see this is a stupid idea. Thanks!

https://gist.github.com/carasmo/d8dc0d33a2a54a2945aa47703ee5b3df