Capture URL with iframe form

[Giarc86]

Hi Guys,

I have an iframe from a company that handles our forms.
We are needing the form to be able to capture the current pages' URL and send it with the form to their system.

Can this method work or is there some other way to do it?
I Googled and saw that $_SERVER[REQUEST_URI]; will capture a pages' URL

<iframe src="http://www.iframesource.co.za/references/resource?dfgonRN0&addNote=<?php echo $_SERVER[REQUEST_URI]; ?>" width="100%" height="600">
  <p>Your browser does not support iframes.</p>
</iframe>

Thanks for any advice.