array elements overwriting not appending

[Anon]

I am trying to create a shopping cart application. My cart is a class, registered as a session variable. The class has a variable $items which is a multidimensional array containing the productid and another array containing the detail info about the item. It works fine adding an item. However, when I add additional items, each one just overwrites the array instead of appending a new element.

Here's the basic code:
Class Cart
{
var $items;
var $product_total;
var $shipping_total;
var $tax_total;
var $cart_id;

function add($sell_price,$qty,$shipping,$tax,$productid,$short_desc,$note)
{
if (isset($this->items[$productid])) //if it is already in the cart, don't add a new occurence, just update the total quantity
{

$this->items[$productid]["quantity"] += $qty;
}
else
{
$this->items[$productid]=array(
"price"=>$sell_price,
"quantity"=>$qty,
"shipping"=>$shipping,
"tax"=>$tax,
"desc"=>$short_desc,
"note"=>$note);
$this->product_total = $this->product_total += $sell_price;
$this->shipping_total = $this->shipping_total += $shipping;
}

} //end add

This whole multidimensional array has been giving me fits, but I think it's the best solution to this problem (if I can get it to work!)
Any thoughts on the subject?

Thanks,
Sheila

[[deleted]]

The only way this could 'overwrite' existing items is if the $productid is the same all the time.

As with all debugging: print the vars you are using. Print them and see if they make any sense. Especially the arrays are difficult to understand, so print them!

echo '<pre>';
print_r($aArray);
echo '</pre>';

PS I would advice agains storing the totals in the session. It is common practice to calculate those on the fly. (saves you work, and gives less chance of errors)

[Anon]

In doing a little more debugging (printing vars is my usual method also) I find that somehow, the array $this->items (or $sess_cart->items in the main.php) is empty every time I call the add method. I've printed it in the main script (which does the db lookup and returns the item info to pass to the add method) and at the beginning of the add method, and it's empty both times. I have the class Cart defined as a session variable, and the lines
require_once("./include/cart.php");
session_start();

at the beginning of every script. I've checked to be sure that new Carts aren't getting created every time (the $this->cart_id variable stays the same). Any idea why my items array keeps getting hosed?

(PS thanks for pointing out the totals issue. In fact, I do recalculate them every time the cart displays. I've been staring at the array add issue for so long, I lost track of that bit of redundancy!)

Thx,
sheila

[[deleted]]

Do you also have 'error_reporting(E_ALL)' at the top of your script?

[Anon]

No, I'd never used that. I'm working with it now and wading my way through seemingly endless 'undefined variable' errors. This is very enlightening. I guess PHP is a lot more forgiving than I thought.

[Anon]

Vincent,
Thanks for your suggestions. The error_reporting(E_ALL) was very enlightening and pointed out some sloppy coding.

My original problem is now redefined. It's not that the array is being overwritten, it's apparently being redefined each time the add method executes. I'm getting the error 'Undefined property: items' from both the cart.php and the main.php. I'm wondering if it's something in the session? I'm still experimenting but welcome any ideas.

Thanks,
Sheila

[Anon]

I finally found a reference on php.net that told me that session variables called from within a function (as in my main.php, which did things like $sess_cart->add($item,$qty,$price) has to defined those session variables as globals. This seems counter-intuitive to me; isn't the whole point of sessions to have things available across pages? Why should you have to explicitly declare them global? Seems like they'd be global by default.

But anyway, after I did that, all my array functions worked like a charm.