Hey, I am learning from one of Sitepoint’s books PHP & MySQL Novice to Ninja by Kevin Yank and encountered a funny problem. The example itself in the book is incorrect and the source code of the book is not working either.
Here I am making a Shopping Cart. The problem is that once you put items in the shopping cart in ‘catalog.html.php’ page and store them in a variable $_SESSION[‘cart’], it becomes empty and stops holdings all its values when I go to the next page ‘cart.html.php’ where I should be able to check all the items I bought. I don’t understand fully enough how sessions work thus I have no idea how to debug it. Could you explain what is the problem?
index.html :
<?php
include_once $_SERVER['DOCUMENT_ROOT'] .
'/includes/magicquotes.inc.php';
$items = array(
array('id' => '1', 'desc' => 'Canadian-Australian Dictionary',
'price' => 24.95),
array('id' => '2', 'desc' => 'As-new parachute (never opened)',
'price' => 1000),
array('id' => '3', 'desc' => 'Songs of the Goldfish (2CD set)',
'price' => 19.99),
array('id' => '4', 'desc' => 'Simply JavaScript (SitePoint)',
'price' => 39.95));
session_start();
if (!isset($_SESSION['cart']))
{
$_SESSION['cart'] = array();
}
include 'catalog.html.php';
if (isset($_POST['action']) and $_POST['action'] == 'Buy')
{
// Add item to the end of the $_SESSION['cart'] array
$_SESSION['cart'][] = $_POST['id'];
header('Location: .');
exit();
}
if (isset($_POST['action']) and $_POST['action'] == 'Empty cart')
{
// Empty the $_SESSION['cart'] array
unset($_SESSION['cart']);
header('Location: ?cart');
exit();
}
if (isset($_GET['cart']))
{
$cart = array();
$total = 0;
foreach ($_SESSION['cart'] as $id)
{
foreach ($items as $product)
{
if ($product['id'] == $id)
{
$cart[] = $product;
$total += $product['price'];
break;
}
}
}
include 'cart.html.php';
exit();
}
cart.html.php :
<?php include_once $_SERVER['DOCUMENT_ROOT'] .
'/includes/helpers.inc.php'; ?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Shopping Cart</title>
<style>
table {
border-collapse: collapse;
}
td, th {
border: 1px solid black;
}
</style>
</head>
<body>
<h1>Your Shopping Cart</h1>
<?php echo count($_SESSION['cart']); ?>
<?php if (count($cart) > 0): ?>
<table>
<thead>
<tr>
<th>Item Description</th>
<th>Price</th>
</tr>
</thead>
<tfoot>
<tr>
<td>Total:</td>
<td>$<?php echo number_format($total, 2); ?></td>
</tr>
</tfoot>
<tbody>
<?php foreach ($cart as $item): ?>
<tr>
<td><?php htmlout($item['desc']); ?></td>
<td>
$<?php echo number_format($item['price'], 2); ?>
</td>
</tr>
<?php endforeach; ?>
</tbody>
</table>
<?php else: ?>
<p>Your cart is empty!</p>
<?php endif; ?>
<form action="?" method="post">
<p>
<a href="?">Continue shopping</a> or
<input type="submit" name="action" value="Empty cart">
</p>
</form>
</body>
</html>
catalog.html.php :
<?php include_once $_SERVER['DOCUMENT_ROOT'] .
'/includes/helpers.inc.php'; ?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Product Catalog</title>
<style>
table {
border-collapse: collapse;
}
td, th {
border: 1px solid black;
}
</style>
</head>
<body>
<p>Your shopping cart contains <?php
echo count($_SESSION['cart']); ?> items.</p>
<p><a href="?cart">View your cart</a></p>
<table border="1">
<thead>
<tr>
<th>Item Description</th>
<th>Price</th>
</tr>
</thead>
<tbody>
<?php foreach ($items as $item): ?>
<tr>
<td><?php htmlout($item['desc']); ?></td>
<td>
$<?php echo number_format($item['price'], 2); ?>
</td>
<td>
<form action="" method="post">
<div>
<input type="hidden" name="id" value="<?php
htmlout($item['id']); ?>">
<input type="submit" name="action" value="Buy">
</div>
</form>
</td>
</tr>
<?php endforeach; ?>
</tbody>
</table>
<p>All prices are in imaginary dollars.</p>
</body>
</html>
Now it also says “Cannot modify header information - headers already sent by…”. The code is copied straight from the source code (