function group_add_user($group,$user){
        //adding a user is a bit fiddly, we need to get the full DN of the user
        //and add it using the full DN of the group
        
        //find the user's dn
        $user_info=$this->user_info($user,array("cn"));
        if ($user_info[0]["dn"]==NULL){ return (false); }
        $user_dn=$user_info[0]["dn"];
        
        //find the group's dn
        $group_info=$this->group_info($group,array("cn"));
        if ($group_info[0]["dn"]==NULL){ return (false); }
        $group_dn=$group_info[0]["dn"];
        
        $add=array();
        $add["member"] = $user_dn;
        
        $result=@ldap_mod_add($this->_conn,$group_dn,$add);
        if ($result==false){ return (false); }
        return (true);
    }