Canonical for pagination in Opencart below version 3

Pagination pages may not have canonicals at all by default. To add their automatic generation, open the file /catalog/controller/product/category.php and in it after the line $this->load->model(‘tool/image’); add the following code:

if (isset($this->request->get['page'])) {
            $page = $this->request->get['page'];
            $pathx = explode('_', $this->request->get['path']);
            $pathx = end($pathx);
            $this->document->addLink($this->url->link('product/category', 'path=' . $pathx ), 'canonical');
        } else {
            $page = 1;
        }