从会话购物车中读取多个项目时出现问题

Question

I'm kind of new to PHP and I built a page from scratch. I found out a shopping cart code online which I took and use and works perfectly fine:

if(isset($_POST["add_to_cart"]))
{
    if(isset($_SESSION["shopping_cart"]))
    {
        $item_array_id = array_column($_SESSION["shopping_cart"], "item_id");
        if(!in_array($_GET["id"], $item_array_id))
        {
            $count = count($_SESSION["shopping_cart"]);
            $item_array = array(
                'item_id'           =>  $_GET["id"],
                'item_name'         =>  $_POST["hidden_name"],
                'item_price'        =>  $_POST["hidden_price"],
                'item_quantity'     =>  $_POST["quantity"]
            );
            $_SESSION["shopping_cart"][$count] = $item_array;
        }
        else
        {        }
        
    }
    else
    {
        $item_array = array(
            'item_id'           =>  $_GET["id"],
            'item_name'         =>  $_POST["hidden_name"],
            'item_price'        =>  $_POST["hidden_price"],
            'item_quantity'     =>  $_POST["quantity"]
        );
        $_SESSION["shopping_cart"][0] = $item_array;
    }
}

if(isset($_GET["action"]))
{
    if($_GET["action"] == "delete")
    {
        foreach($_SESSION["shopping_cart"] as $keys => $values)
        {
            if($values["item_id"] == $_GET["id"])
            {
                unset($_SESSION["shopping_cart"][$keys]);
                echo '<script>window.location="grid.php"</script>';
            }
        }
    }
} 

This let me add multiple products, quantity and price to a cart. What I'm now trying to do is create purchase orders from that purchase detail, lets say someone buys 2 products, I need to insert into SQL table 2 rows, one for each product.

after some Google, I figured I'd have to use a foreach and I ended up with this:

$_SESSION['shopping_cart'][] = $result;
foreach ($_SESSION['shopping_cart'] as $result){
    echo "Item id:  ".$result['item_id']." , <br>\n 
          cantidad: ".$result['item_quantity']." ,<br>\n 
          Precio unitario: ".$result['item_price']."<br>\n";
}

this returns the next error on the page :

Notice: Trying to access array offset on value of type null in C:\xampp\htdocs\PHP\Proyecto\Crear_OC.php on line 79

Notice: Trying to access array offset on value of type null in C:\xampp\htdocs\PHP\Proyecto\Crear_OC.php on line 80

what I'm trying to do is echo all the products with quantity, total and unit price to see if I was getting them right, if I can do that then I have this code to execute the inserts into SQL :

$total = $total + ($values["item_quantity"] * $values["item_price"]);
    $sql="  INSERT INTO ordenes_ventas (ID_Producto,ID_Cliente,Precio_Unitario,Cantidad,Monto)
                    select p.ID_Producto,C.ID_Cliente,p.Precio_Unidad, $result['item_quantity'],$total 
                    from productos p 
                    join clientes c 
                    on c.ID_Cliente = (select c.ID_Cliente from clientes c where c.Users = '$user') 
                    where p.ID_Producto = $result['item_id'] ";

    if ($conexion->query($sql) === TRUE) {
    echo 'Succesful!';
    } else {
    echo "Error: " . $sql . "<br>" . $conexion->error;
}
}

Answer 1

What you want to do is to use the session number in the shopping cart and perform a MySQL statement to find the items that the customer has been shopping for. This insures that if two customers are using the cart at the same time their orders aren't confused and load at the same time.

I am including some code I have done on a project that you can look at to incorporate into your code.

You need to capture the session number for the individual:

/*insert the content into the cart table*/
        $addCart = 'INSERT INTO cart (cartId, productId, quantity_order, sessionNumber) VALUES ("","'.$productId.'","'.$quantity.'","'.$sessionNumber.'")';

After you have the items in your cart you can now use another SQL statement to find the current items in the customers cart.

$findCart = "SELECT p.productId, p.name, p.image, p.price, p.quantity, c.cartId, c.quantity_order, c.sessionNumber FROM product p, cart c WHERE p.productId = c.productId AND c.sessionNumber = '$sessionNumber' "; 

I think this method will be much smoother than an array statement.