ROOT in login.php ( error or not error )

[gAp]

In a file login.php from last SVN
have code on line 20:

// Checking path
$pathServer = preg_replace('!^/!', '', $_SERVER['PHP_SELF']);
$pathUser = preg_replace('!^/!', '', str_replace($_SERVER['DOCUMENT_ROOT'], '', $_SERVER['SCRIPT_FILENAME']));
if (strcmp($pathServer, $pathUser))
...

In my surroundings DOCUMENT_ROOT = '/',
then the function str_replace will be replaced '/' to ' '.
As a result of an error:

Path is not the same between your browser and you server :
- Server:
shop/admin23/login.php
- Browser:
homewwwXXXX.XXshopadmin23login.php
==================================

Donc, si je pas raison?
D'erreur s'affiche encore.