Storing multiple values in a $_SESSION variable with PHP

Question

I'm creating a site which has a shopping cart. I do not need any special functionality so I'm creating the cart on my own rather than integrating any ready one. My products do not have a predefined price in the database. The price is being generated dynamically based on the values entered by a user on the product page. So, the user chooses some specifications, enters the quantity and I get the following values:

Item ID
Quantity
Total price

I need to store those values in the $_SESSION variable and then loop over it when needed to get the results and print them in the shopping cart. The problem is that there are a lot of products and I need to store all those values (Quantity, Total Price) distinctively for the chosen product. That said, how do I store Item ID, Quantity and Total price in the $_SESSION variable and associate those values with each other?

Thanks for helping.

EDIT: My code implementing Michael's suggestions:

$itemid = $db->escape($_POST['productid']);
    $itemquantity = $db->escape($_POST['itemquantity']);
    $totalprice = $db->escape($_POST['totalprice']);

    $_SESSION['items'] = array();

    $_SESSION['items'][$itemid] = array('Quantity' => $itemquantity, 'Total' => $totalprice);

    var_dump($_SESSION);

Solution

Use the item ID as an array key, which holds an array of the other items:

// Initialize the session
session_start();

// Parent array of all items, initialized if not already...
if (!isset($_SESSION['items']) {
  $_SESSION['items'] = array();
}

// Add items based on item ID
$_SESSION['items'][$itemID] = array('Quantity' => $quantity, 'Total' => $total);
// Another item...
$_SESSION['items'][$another_itemID] = array('Quantity' => $another_quantity, 'Total' => $another_total);
// etc...

And access them as:

// For item 12345's quantity
echo $_SESSION['items'][12345]['Quantity'];

// Add 1 to quantity for item 54321
$_SESSION['items'][54321]['Quantity']++;

Comments

[cycero]

Thanks Michael! However this erases the existing values in the $_SESSION variable. Say, I've added one set of values with $itemID=29 and then when I add another one with $itemID=30 my $_SESSION variable contains only the last set of data.

[Michael Berkowski]

@cycero Not so. $_SESSION['items'] is an array. Each time you add an item to it with $_SESSION['items'][$newitemID] you're adding to the array, not overwriting the previous one.

[cycero]

When I do a simple print_r($_SESSION) it prints only the last set of values, not all.

[Michael Berkowski]

@cycero Post your current code implementing what I have above, and the var_dump($_SESSION)

[cycero]

I've updated my question with the code which returns only the last result set.

[Michael Berkowski]

@cycero I see - it's because you're calling $_SESSION['items'] = array() each time before adding a new item. You're re-initializing the array each time so only the last item appears there. Just call $_SESSION['items'] = array(); one time at the very beginning before any items have been added, and don't call it again.

[cycero]

Thanks for helping me, Michael. But it still does not work as expected even if I completely remove $_SESSION['items'] = array(); from the code.

[Michael Berkowski]

@cycero And you have called session_start()? I made a couple of additions above..

[cycero]

Thanks Michael! My fault, I forgot about session_start(); This works fine now.

[Shackrock]

@cycero And I'd be careful about storing HUGE arrays here. It's generally not great practice to store tons of things in the session variable...

[Gem]

@MichaelBerkowski I am working with PHP Add-To-Cart module using SESSION, if i click add to cart button only one product will be added to cart, how can i use to add more than one products added to the cart using session? my code : pastiebin.com/5d25daaf24674 thanks.

[Michael Berkowski]

@Gem That is too broad to be addressed in an old question's comment thread. You should post a new question, reference this one if you are attempting to apply it to your situation.