opencart category son eklenenlere göre sıralama

In the catalog/controller/product/category.php if have changed the following lines:
from:

$sort = 'p.sort_order';

to:

Code: Select all

$sort = 'p.date_modified';

from:

Code: Select all

$order = 'ASC';

to:

Code: Select all

$order = 'DESC';

from:

Code: Select all

'value' => 'p.sort_order-ASC',

to:

Code: Select all

'value' => 'p.date_modified-DESC',

from:

Code: Select all

'href'  => $this->url->link('product/category', 'path=' . $this->request->get['path'] . '&sort=p.sort_order&order=ASC' . $url)

to:

Code: Select all

'href'  => $this->url->link('product/category', 'path=' . $this->request->get['path'] . '&sort=p.date_modified&order=DESC' . $url)

In the catalog/model/catalog/product.php I have changed the following lines…
from:

Code: Select all

$sql .= " GROUP BY p.product_id";
			
			$sort_data = array(
				'pd.name',

to:

Code: Select all

$sql .= " GROUP BY p.product_id";
			
			$sort_data = array(
				'p.date_modified',

from:

Code: Select all

if ($data['sort'] == 'pd.name' || $data['sort'] == 'p.model') {

to:

Code: Select all

if ($data['sort'] == 'p.date_modified' || $data['sort'] == 'p.model') {

from:

Code: Select all

$sql .= " ORDER BY p.sort_order";

to:

Code: Select all

$sql .= " ORDER BY p.date_modified";

But changing these still does not show product by date_modified when I load any category & even when I change the sort & the select default, the address bar shows as

sort=p.date_modified&order=DESC

, but the products are not showing by date_modified, so I must be missing something & hope somebody can help?
Regards