How to have a session that never expires ?

The problem is here

PHP Code:

$config['sess_save_path'] = NULL; 


When using the file driver the value must be an absolute path to the folder to be used for the session files.

Read the Files Driver Documentation until you see the comment about absolute paths.

Thanks for the info !  
But i don't get it, actually when $config['sess_save_path'] is empty, the default path is "/srv/data/var/php/www" as you can see in my phpinfo()
Do i need to copy/past that in the $config['sess_save_path'] or do i need to create another custom folder ? 

Thanks a lot for your help !!