//hidden directory of the group if the user is not a member of the group
//show group's directory only if I'm member. Or if I'm a teacher. TODO: check groups not necessary because the student dont have access to main folder documents (only to document/group or document/shared_folder). Teachers can access to all groups ?
$group_folder='_groupdocs';
//show group's directory only if I'm member. Or if I'm a teacher