final protected function auth($member)
    {
        if ($member) {
            $this->session->set('auth_member_id', $member->getId());
        } else {
            $this->session->remove('auth_member_id');
        }
        return $this;
    }
final protected function auth($member)
    {
        if ($member) {
            $this->session->set('auth_member_id', $member->getId());
        } else {
            $this->session->remove('auth_member_id');
        }
        return $this;
    }
final protected function auth ( $ member ) { if ( $ member ) { $ this -> session -> set ( 'auth_member_id' , $ member -> getId ( ) ) ; } else { $ this -> session -> remove ( 'auth_member_id' ) ; } return $ this ; }
set auth user to session

@param null|Member $member
@return $this
set auth user to session