A BIG ATTENTION!
let`s say that we have this 2 files include.php & test.php:
include.php
<?
$foo="blabla";
?>
and now test.php:
<?
require "include.php";
function do_test()
{
if ($foo) {echo "foo is set if called from function<br>";} else {echo "bang foo is not set if called from function<br>";}
}

do_test();
if ($foo) {echo "foo is set if called from main<br>";} else {echo "bang foo is not set if called from main<br>";}
Result of the program is:
bang foo is not set if called from function.
foo is set if called from main

Bug?
Server: Apache/1.3.26 (Win32) PHP/4.2.3