Swfobject as3 issue

I’m writing the following code to embed an swf file into php file.

[AS] var so = new SWFObject(“test.swf”, “mymovie”, “1152”, “700”, “8”, “#FFFFFF”);
so.addVariable(“varurl”, “http://www.google.com”);
so.write(“flashcontent”);[/AS]

but I don’t know how to access the variable “varurl” that i’ve added in the second line above. In flash 8 with AS2, I would just use _root.varurl. But it doesn’t seem to work in AS3.