URL querystring values (simple problem)

I have the most basic problem. I am trying to pass a value from a url/querystring like http://test/test.php?example=11 so now how to I get it in a <input type="text" name="example"> on a page called test.php. This must be so simple and I am overdoing it. I am generating this url to be sent in an email to people and I want this value in a form text box to make it easy for the user and all they have to do is hit submit. Thanks, Frank