setting php variables from the client side

I'm still struggling a bit with sessions and state. What I think I'm trying to do is use a Javascript onclick to call a created function that will set session variables and then load a new page. Is it possible to set php variables from the client side with out passing them in the "url.html?var1=value&var2=value" format? I'm also getting killed because form variables don't change session variables with the same name (it took many hours to figure this out!). Am I going about this the wrong way...is there an easier method? Thanks, Ron