Why not pass as a parameter and/or use return values? Your application shouldn't need to reply on globals, and is usually a sign of a design flaw.
function getVar() {
return array('some'=>'values');
}
function printVar($var) {
include_once('myfile.php');
// print_r($var);
}
$var = getVar();
printVar($var);
If your problem is larger than the example shows, you should take a look at PHP's OOP and start using classes/objects. Check out some frameworks to help you dive right in too.