I tried to update the php version of my VPS but it didn\'t work and my provider didn\'t help me well, so i downgrade it to the previous version.
I am now working wi
Is safe mode activated? That might be your problem...
As of PHP 4.3.0, in order to prevent someone from writing a script which reveals the password for a page that was authenticated through a traditional external mechanism, the PHP_AUTH variables will not be set if external authentication is enabled for that particular page and safe mode is enabled. Regardless, REMOTE_USER can be used to identify the externally-authenticated user. So, you can use $_SERVER['REMOTE_USER'].
Source: http://php.net/manual/en/features.http-auth.php
I finally found the answer thanks to 'mbinette'.
In my PHP configuration, the handler of PHP 5 was CGI, and this type of authentication doesn't work with PHP CGI. So i changed it to suPHP (which is supposed to be the default one on APACHE).
Find here a post explaining a way to use CGI and PHP_AUTH, but i tried and it wasn't working.
Find here some explanations about php handlers