Rules: how to create variable with PHP and $_SERVER['HTTP_REFERRER']
Turns out I just had to look harder and change my expectations a little.


Click Add a Variable
Select text (for my scenario)
In the Value field, you can then use php to echo out a value for a single variable


I was hoping to be able to create a variable with a type of 'object' (or similar) so that I could use the url values like [url:param1] or [url:param2].  

I have not found a way to do that - I just created a different variable for each of the two parameters I needed off the query string.