Can't delete my first item in shopping basket - php

Question

Currently doing my computing science assignment and I've chosen to make an online shop, I've used a tutorial to make the shopping basket and everything is working except I can only delete every item except the first one added to my cart. I'd really appreciate any help if possible.
This is where items in my cart are displayed (cart.php):
<?php
session_start();
require_once('db.php');
include('common.php');
?>
<?php getHeader(); ?>
<div class="container">
<div class="row">
<table class="table">
<?php
$items = $_SESSION['cart'];
$cartitems = explode(",", $items);
?>
<?php
$total = '';
$i=1;
foreach ($cartitems as $key=>$id) {
$sql = "SELECT * FROM products WHERE id = $id";
$res = mysqli_query($con, $sql);
$r = mysqli_fetch_assoc($res);
?>
<tr>
<td><?php echo $i; ?></td>
<td>Remove <?php echo $r['name']; ?></td>
<td>£<?php echo $r['price']; ?></td>
</tr>
<?php
$total = $total + $r['price'];
$i++;
}
?>
<tr>
<td><strong>Total Price</strong></td>
<td><strong>£<?php echo $total; ?></strong></td>
<td>Checkout</td>
</tr>
</table>
</div>
</div>
<?php getFooter(); ?>
This is my code that adds an item to my cart(addtocart.php):
<?php
session_start();
if(isset($_SESSION['cart']) & !empty($_SESSION['cart'])){
$items = $_SESSION['cart'];
$cartitems = explode(",", $items);
$items .= "," . $_GET['id'];
$_SESSION['cart'] = $items;
header('location: index.php?status=success');
}else{
$items = $_GET['id'];
$_SESSION['cart'] = $items;
header('location: index.php?status=success');
}
if(in_array($_GET['id'], $cartitems)){
header('location: index.php?status=incart');
}else{
$items .= "," . $_GET['id'];
$_SESSION['cart'] = $items;
header('location: index.php?status=success');
}
?>
This is my delete item code (delcart.php):
<?php
session_start();
$items = $_SESSION['cart'];
$cartitems = explode(",", $items);
if(($_GET['remove']) & !empty($_GET['remove'])){
$delitem = $_GET['remove'];
unset($cartitems[$delitem]);
$itemids = implode(",", $cartitems);
$_SESSION['cart'] = $itemids;
}
header('location:cart.php');
?>

Answer 1

The problem is this line:
if ($_GET['remove'] & !empty($_GET['remove']))
When you want to remove the first item, $_GET['remove'] is 0, which is falsey and also considered empty, so the code that's supposed to remove it doesn't run. Change it to:
if (isset($_GET['remove']) && is_numeric($_GET['remove']))
Also, throughout your scripts you're using & when you should be using &&. & is bit-wise AND, && is logical AND.

Answer 2

When you have only one item in your session,
$cartitems = explode(",", $items);
result is array with "0" index, so if you want to remove last value, $_GET['remove'] should be equal to "0" (example: www.site.loc/?remove=0)
I hope you show us only a sample (not production) code because it is very wrong written and dangerous example:
$sql = "SELECT * FROM products WHERE id = $id"; SHOULD NEVER BE USE!

Answer 3

There's a few things wrong with your code:
1) $_SESSION['cart'] appears to be a string of comma-separated ids, i.e. string(10) "1, 2, 3, 4"
Thus, $cartitems = explode(",", $items) would return an array of those ids, i.e. array(4)[ 1, 2, 3, 4 ]
2) Assuming that $_GET['remove'] is a string containing the item id, i.e. 3
Calling unset($cartitems[$delitem]) would remove the last element of my example array, 4, since arrays are zero-indexed.
To remove the value 3 you'd have to call:
$delitem = array_search($_GET['remove'], $cartitems);
unset($cartitems[$delitem]);
(see http://php.net/array_search)
3) May I please suggest using PDO? http://php.net/manual/en/book.pdo.php
Edit: since I can't comment, Barmar:
Given that OP's items are stored in a database, and id is likely a primary key, it's unlikely that he'd have an item with id of 0 so empty() should be perfectly suitable for his needs. To expound on that point, though, OP, Barmar is correct that in if there are in fact 0 based ids, you'd want to use isset($_GET['remove']) not !empty($_GET['remove'])
See http://php.net/isset and http://php.net/empty for differences.

Answer 4

Your loop and then usage of the variables is the problem:
foreach ($cartitems as $key=>$id) {
...
<td>Remove <?php echo $r['name']; ?></td>
...
}
The $key should be $id
When using foreach this way, the $key var is the array index and the $id is the value (which could be a string, array, object, int...).
http://php.net/manual/en/control-structures.foreach.php
But since you don't care about the array index here, you can simply omit it from the foreach declaration:
foreach ($cartitems as $id) {
and it will work identically.