Q:

$_GET[] doesn't work in included file? 

I have a webpage which holds the number of the page to display:
mydomain.net/index.php?page=42

This works alright.  Now I want to display the page only when a particular cookie is set, and I moved most of the body to an include file, so that index.php only has
<? php 
    if ($cookie_ok):
        include("http://mydomain.net/index_d6skrif9.php"); 
    else:
        include("http://mydomain.net/noaccess.inc"); 
    endif 
? >

and now the $_GET["page"] in the include file, which is supposed to retrieve the page number returns nothing.  
I read that $_GET[] is a superglobal and that superglobals' scopes are across include files.  So what's wrong here, and how can I use the page number in the include file? 

A:

$_GET works in included files, it does not work in included HTTP resources. 
The PHP in index_d6skrif9.php will be executed by mydomain.net before it gets to the PHP program with the include statement in it. 
Use a local file path, not an HTTP URL. 
include("index_d6skrif9.php"); 

Alternatively, pass the value to the server you are pulling the include from:
include("http://mydomain.net/index_d6skrif9.php?page=" + urlencode($_GET['page'])); 

Note that the latter approach has far more opportunity for things to go wrong and is much less efficient than a local file included, so it isn't recommended if you can help it. 

A:

You'll need to include them locally, not over-the-web:
if ($cookie_ok) 
    include("index_d6skrif9.php"); 
else
    include("noaccess.inc"); 
endif 

By using URLs, you're making a web-request and the server executes the PHP in the file and returns the contents (making it have its own set of super-globals).