public function groupAddMember($group_dn, $user) {

    $user_ldap_entry = $this->userUserToExistingLdapEntry($user);
    $result = FALSE;
    if ($user_ldap_entry && $this->groupGroupEntryMembershipsConfigured) {
      $add = array();
      $add[$this->groupMembershipsAttr] = $user_ldap_entry['dn'];
      $this->connectAndBindIfNotAlready();
      $result = @ldap_mod_add($this->connection, $group_dn, $add);
    }

    return $result;
  }