How can I pass variable and parse it on other php page?

I have variable <%city%> which will show on my template page fine.

Now I want to use my php page which will draw a image based on "city" variable.

http://www.test123.com/...map.php?city=toronto

above works fine. Now How do I include this on my template pages?

<%include http://www.test123.com/...city=<%city%>%>

Obviously above does not work, but maybe it shows what I am after

Thanks