src/Dlin/Zendesk/Result/PaginatedResult.php
public function getPreviousResult(){
        if($this->getCurrentPage() > 1){
            return $this->client->getCollection($this->getEndPoint(), 'tickets', $this->getCurrentPage()-1, $this->getPerPage());
        }
        return null;
    }
public function getPreviousResult(){
        if($this->getCurrentPage() > 1){
            return $this->client->getCollection($this->getEndPoint(), 'tickets', $this->getCurrentPage()-1, $this->getPerPage());
        }
        return null;
    }
Note: the web service never return next page URL, this method overrides the next_page url and resets the current pages param
@return $this