[PHP] losing session variable

[Alain Roger]

Hi,

I have the following code :

   session_start();

    $_SESSION['username']=$myusername;
    $_SESSION['Localization'] = $lang;
    header("Location:
https://".$_SERVER['SERVER_NAME'].$path_adm_files."/modules/welcome/welcome.php");

if i check before header command what is the value of $_SESSION['username'],
i get the right value.
however, if i place on the first line of welcome.php file the following code
:

echo "<br>1. Before session";

session_start();
echo"<br>Username : ".$_SESSION['username'];
echo "<br>2. After session";

i get empty value for this session variable.
How is it possible ?

in my first code piece, if i use localhost instead of
$_SERVER['SERVER_NAME'], it creates a session file in my temporary folder as
it should be....
I'm confused now :-(

thanks a lot for your help.
--
Alain
------------------------------------
Windows XP SP2
PostgreSQL 8.1.4
Apache 2.2.4
PHP 5.2.1