Как переделать sql запрос в php переменные?

Без set

$customer_new = $this->db->query("
   SELECT tb03.customer_id, tb01.product_id, sum(tb01.quantity) AS sum_quantity
   FROM oc_order_product AS tb01
   LEFT JOIN oc_order AS tb02 ON tb01.order_id = tb02.order_id 
   LEFT JOIN oc_customer AS tb03 ON tb02.customer_id = tb03.customer_id
   WHERE tb03.customer_id = '{$cid}'
   GROUP BY tb03.customer_id, tb01.product_id
");

UPD: Если я правильно понял документацию, то должно быть так

$cid = (int)$this->customer->getId();
$pid = (int)$product_query->row['product_id'];
$customer_new = $this->db->query("
  SELECT tb03.customer_id, tb01.product_id AS prod_id, sum(tb01.quantity) AS sum_quantity
  FROM oc_order_product AS tb01
  LEFT JOIN oc_order AS tb02 ON tb01.order_id = tb02.order_id 
  LEFT JOIN oc_customer AS tb03 ON tb02.customer_id = tb03.customer_id
  WHERE tb03.customer_id = '{$cid}'
  GROUP BY tb03.customer_id, tb01.product_id
");
$rows = $customer_new->rows;
$ssd = array();
foreach($rows as $index => $row){
  $ssd[] = array(
    'prod_id' => $row['prod_id'], 
    'sum_quantity' => $row['sum_quantity']
  );
}
print_r($ssd);