Description:
------------
mkdir() will fail, if open_basedir restricts the access to a path which is only a link, but not a real path.

Reproduce code:
---------------
Directory structure:
/path/
 `- htdocs/
   `- mkdir.php
   `- var/ -> /path/var
 `- var/

Ini settings:
open_basedir = '/path/htdocs:/path/var';

Code: (mkdir.php)
<?php
// This will work on Linux, BSD, but not on Solaris
mkdir('/path/htdocs/var/testdir');

Expected result:
----------------
Creating the directory.

Actual result:
--------------
Warning: mkdir(): open_basedir restriction in effect. File(/path/htdocs/var/testdir) is not within the allowed path(s): ('/path/htdocs:/path/var') in /path/htdocs/mkdir.php on line 2