I am using an Aug 6th cvs build of php4 on apache-1.3.26.  I have chrooted apache and I also wanted to use open_basedir to help improve security between users.  My open_basedir is set to "/www/admin/:/www/global.include/", and to test open_basedir i created /www/admin/basedir.php which contains:
<?php
echo 'Include test<br>'
include("/etc/resolv.conf");
echo '<br><br>Readfile test <br>';
echo readfile("/etc/resolv.conf");
?>
The result is the printing of my nameservers from outside the open_basedir.  I do however get a open_basedir warning for trying to open outside files using fopen/fread and also readdir, but not with include(), include_once(), or readfile().