How do I properly pass an url with get variables as a get variable?

Question

So, I have a link like this...

http://my-affiliate.com?pr=9&user=274934&ad_id=12598

And I am trying to pass it through a link with get variables, such as...

http://my-website.com/ad-tracking.php?userID=1&link=http://my-affiliate.com?pr=9&user=274934&ad_id=12598

But when I do that, it recognizes the affiliate's get variables as my own. So, the link get variable turns out to be http://my-affiliate.com?pr=9.

How can I fix this? I appreciate it. Thank You.