Need help with checkbox

Hello there
Bit of a problem here; I have a html form with a agree/disagree checkbox that needs to be required before submission.

I've made several text fields required no problem, and I know I can use a somewhat simple java script do achieve what I want, but I would rather write it into my existing PHP script......i've tried to make it required the same way I have my text fields, but when I do that, it errors(with my error msg for an unchecked box) every time i try to submit, whether the checkbox is checked or not


please help

Can you share the bits of code that you've got thus far? It would be somewhat easier to show you how to do it in your code than building an example from scratch.