readfile("http://www.foo.org:8000") produces the following error: 

Warning: readfile("http://www.foo.org:8000") - Undefined error: 0 in /usr/home/manero/public_www/sc.php on line 5

I'm not sure if readfile() can take cgi arguments either, such as:

readfile("http://www.foo.org/horsey.php?arg1=one&arg2=two");

Maybe it's just a feature in that it doesn't take a port, but it seems like it would be useful to be able to do this sort of thing.