php, $_SERVER & server_name

[AMP Admin]

I'm trying to list a bunch of domains under server_name.  I'm doing this
because these domains generate dynamic content based on their name.  it
seems to work fine except for one thing... $_SERVER['SERVER_NAME'] just
displays the first server_name entry. 

So say we have the following:

server_name 	*.example1.com *.example2.com *.example3.com;

echo $_SERVER['SERVER_NAME']; displays *.example1.com regardless which
domain was entered into the browser. 

Regards, 

-Team AMP 
http://www.ampprod.com