gistfile1.php

// next
         $select->from(
                    array(
                        'photos' => $this->_name
                    ),
                    array(
                        'photo_id', 'fk_user_id'
                    )
                )
                ->where('photo_id > ?', $id)
                ->limit(1);

// prev just switch the where clause photo_id < ?