Update Data stock after the purchase on CodeIgniter with Library Cart

Question

I am trying to build an e-commerce system but I can constraints, so when The purchase of goods then the database will reduce the field of stock, after I try, but the result does not fit, what's wrong?

Controllers

function purchase {
        foreach($this->cart->contents() as $item)
        {
            $data = array(
                    'id_product' => $item['id'],
                    'name_product' => $item['name'],
                    'quatity'       => $item['qty'],
                    'price'     => $item['price'],
            );

        $data = array(  
                    'stock' => -$item['qty']    
                    );  
        $this->db->where('id_product', $item['id']);
        $this->db->update('tbproduct', $data);  

        }

}

Answer 1

Did you try like this....

$items = $this->cart->contents();
function purchase {
        foreach( $items as $item)
        {
            $stock=$item['stock']-$item['qty'];

            $data = array(
                    'id_product' => $item['id'],
                    'name_product' => $item['name'],
                    'quatity'       => $item['qty'],
                    'price'     => $item['price'],
                    'stock' => $stock
            );

        $this->db->where('id_product', $item['id']);
        $this->db->update('tbproduct', $data);  

        }

}