the best way to store quantity in $_SESSION - php

Question

I have the following function to add products to shopping cart:
function AddToCart($pid)
{
$_SESSION['products'][]['product_id'] = $pid;
}
What is the best way to store product quantity to the same array with the product id, since the array after the ['products'] generates automatically I'm confused how can I assign quantity there? Thank you for your help:)

Answer 1

Why not store all of the information you need at the same time? Here is an excerpt from my own cart:
// add item to cart
$_SESSION['cart'][] = array('product_id' => $product_id,
'cat_id' => $cat_id,
'title' => $title,
'default_img' => $default_img,
'price' => $valid_product['base_price'],
'weight' => $valid_product['weight'],
'length' => $valid_product['length'],
'width' => $valid_product['width'],
'height' => $valid_product['height'],
'surcharge' => $surcharge,
'quantity' => $quantity,
'prop_selection' => $prop_selection,
'po_id' => $po_id,
'stock' => $stock,
'shipper_id' => $valid_product['shipper_id']);

Answer 2

If I understand the question correctly, when AddToCart() is called for a $pid that is already in the array, do you just want it to increment a quantity property for that product? Seems to me you just will need to use an associative array for $_SESSION['products'] instead of a numerically indexed array like you are now:
function AddToCart($pid, $quantity=1) {
if(is_array($_SESSION['products']) && array_key_exists($pid, $_SESSION['products'])) {
$_SESSION['products'][$pid]['quantity'] += $quantity;
} else {
$_SESSION['products'][$pid] = array(
'product_id' => $pid,
'quantity' => $quantity
);
}
}