Question

When I execute this following code for example: cart.php?p=1&action=add

<?php
session_start();

if (isset($_GET['p']) && isset($_GET['action'])) {
$p_id = (int)$_GET['p'];
$action = $_GET['action'];

switch($action) {

    case "add":
        $_SESSION['cart'][$p_id]++;
        echo $_SESSION['cart'][$p_id];//for debug
    break;

    case "remove":
        $_SESSION['cart'][$p_id]--;
        echo $_SESSION['cart'][$p_id];
        if($_SESSION['cart'][$p_id] == 0) unset($_SESSION['cart'][$p_id]);
    break;

    case "empty":
        unset($_SESSION['cart']);
    break;
}
}
?>

I get the following error:

Notice: Undefined offset: 1 in cart.php on line 11

How can i configure the PHP $_SESSION corectly? I

Answer 1

Change this:

$_SESSION['cart'][$p_id]++

to:

$_SESSION['cart'][$p_id] = 1 + (isset($_SESSION['cart'][$p_id]) ? $_SESSION['cart'][$p_id] : 0);

So that you don’t try to increment a non existent element in your array.