[horde] _prefs_hook_from_addr(): inexistant index in $_SESSION

[Florent AIDE]

Hello list, 
 
When I try to use the _prefs_hook_from_addr() hook, in horde/config/hooks.php 
and activate it in horde/imp/config/prefs.php 
 
I use   
 
$cmd = '/usr/bin/ldapsearch -b o=myorg -s sub cn='; 
$cmd .= escapeShellCmd($_SESSION['imp']['user']); 
$cmd .= ' | /usr/bin/grep mail | /usr/bin/awk \'{print $2}\''; 
 
and php answers me: 
 
Notice: Undefined index: imp in /MYPATH/config/hooks.php on line 102 
 
it seems that $_SESSION is not yet existant.... I cannot find the imp index... 
 
Where is the catch ? The comment in the sample hook tell that we can use 
$_SESSION['imp']['user'] 
It even uses it in the sample code... 
 
I also tried to use $_SESSION['__auth']['userID'] but with the same error, the 
script does not find the __auth index 
 
Anyone got an idea ? 
Thanks a lot.