cookie is being overwritten instead of creating a new one - php

Question

I have written the following piece of code which works fine in Firefox.
// add product
if( isset($_GET['add']) ) {
$pointer = 1;
foreach ($_COOKIE['cart'] as $posit => $value) {
$pointer = $posit+1;
}
setcookie('cart['.$pointer.']', $_GET['add'] , time() + 60*60*24*$cookie_cart , '/' );
header('Location: cart.php');
}
The problem was when I tried it with Safari (so I guess the same problem may happen in other browsers. What happens is when the function foreach() runs, Safari reads the cookies in the opposite order Firefox does, so let's say the following cookies are defined: cart[1], cart[2], cart[3]. Firefox goes in this order, so when I add a new one it is stored as cart[4], whilst Safari does the opposite, making $pointer always be 1+1, storing it as cart[2] every time I add a new product.
I have tried many ways of fixing this, but so far unsuccessfully.
Thanks.

Answer 1

It looks like you don't even need a loop, you could just do
$position = count($_COOKIE['cart'])+1;
setcookie('cart['.$position.']',$_GET['add'] , time() + 60*60*24*$cookie_cart , '/' );
Edit:
Even better would be something like this:
function addItem($id) {
$cart = unserialize($_COOKIE['cart']);
$cart[] = $id;
setcookie('cart', serialize($cart) , time() + 60*60*24*$cookie_cart , '/' );
}
function removeItem($id) {
$cart = unserialize($_COOKIE['cart']);
$cart = array_diff($cart, array($id));
setcookie('cart', serialize($cart) , time() + 60*60*24*$cookie_cart , '/' );
}
function getCart() {
$cart = unserialize($_COOKIE['cart']);
return $cart;
}
And then you can just use those functions to interact with your cart.

Answer 2

For getting the next key, I would something simpler like:
//initial value
$newKey = 0;
//if cart is set and is an array
if(isset($_COOKIE['cart']) && is_array($_COOKIE['cart'])){
//get the max value from the keys and add 1
$newKey = max(array_keys($_COOKIE['cart']))+1;
}