The simple answer is that you can't do it.
The slightly more advanced answer is that by using [man]file_get_contents[/man] you can get the evaluated result from the other file. But you can't use functions, variables or other stuff, not even global ones.
The advanced answer is that by compromizing the security of your servers you can do this (at least if I understaood a thread from about 2 weeks ago correctly). But it is not a good idea at all.
The best idea would probably be to have global.php on both servers if possible.