Codeigniter Shopping Cart [closed]

When i create a shopping cart with CI Cart Class, it add the product to the cart first 1 and then when i add that product to the cart next time it is also add 1 product not 2.

I want to do it the quantity in the cart is increased when someone adds an item to their cart and that exact same item is already in the cart.

It would be helpful if you could post some code or what data you are sending to the cart class but this should point you in the right direction:

function add_cart_item(){

        $data = $_POST;

        $id = $data['product_id'];    //get new product id
        $qty = $data['quantity'];     //get quantity if that item       
        $cart = $this->cart->contents(); //get all items in the cart
            $exists = false;             //lets say that the new item we're adding is not in the cart
            $rowid = '';

            foreach($cart as $item){
                if($item['id'] == $id)     //if the item we're adding is in cart add up those two quantities
                {
                    $exists = true;
                    $rowid = $item['rowid'];
                    $qty = $item['qty'] + $qty;
                }       
            }

            if($exists)
            {
                $this->cart_model->update_item($rowid, $qty);                   
                echo 'true'; // For ajax calls if javascript is enabled, return true, so the cart gets updated          
            }
            else
            {
                if($this->cart_model->add_cart_item() == TRUE)
                {           
                    echo 'true'; // for ajax calls if javascript is enabled, return true, so the cart gets updated
                }
            }   

}

and in the cart_model you would have update and add functions that look something like this

function update_item($rowid, $qty){     

        // Create an array with the products rowid's and quantities. 
        $data = array(
             'rowid' => $rowid,
             'qty'   => $qty
          );

    // Update the cart with the new information
        $this->cart->update($data);
    }


    // Add an item to the cart
    function add_cart_item(){

        $id = $this->input->post('product_id'); // Assign posted product_id to $id
        $qty = $this->input->post('quantity'); // Assign posted quantity to $cty
        //$img = $this->input->post('image'); // Assign posted quantity to $img

        $this->db->where('id', $id); // Select where id matches the posted id
        $query = $this->db->get('products', 1); // Select the products where a match is found and limit the query by 1

        // Check if a row has been found
        if($query->num_rows > 0){

            foreach ($query->result() as $row)
            {
                $data = array(
                    'id'      => $id,
                    'qty'     => $qty,
                    'price'   => $row->price,
                    'name'    => $row->name,
                    //'options' => array('image' => $img),
                );

                $this->cart->insert($data); 

                return TRUE;
            }

        // Nothing found! Return FALSE! 
        }else{
            return FALSE;
        }
    }