php add multiple to cart method - php

Question

I am currently able to add a quantity of a product by one or reduce it by one within my cart however I'm trying to add a method whereby I can submit a quantity that I input into a text field.
To increase by one, this is the main part of the code. It is found on the index page.
echo ' Plus 1';
This is the code on the cart page to get that uniquenum and action:
if (isset($_GET['increase1'])) {
$result = 'cart_' . $_GET['increase1'];
$_SESSION[$result] = isset($_SESSION[$result]) ? $_SESSION[$result] + 1 : 0;
}
How could I get the $uniquenum variable from the index page to the cart page using a form and post or get request. If I could do this I could update a quantity. Many thanks in advance.

Answer 1

I'd suggest you put all code belonging to the logic of the cart into a class of it's own. You can then use it as a facade in your code:
// initialize session for Cart
$_SESSION['cart'] || $_SESSION['cart'] = new Cart();
// fetch cart from session
$cart = $_SESSION['cart'];
Then provide methods by cart that offer the functionality you're looking for, either in a simplified form:
$cart->increadeByOne($item);
Or by giving full access to encapsulation of a more differentiated level:
$cart->getItem($item)->getQuantity()->increaseBy($number);
The last example might seem to be bloated, but generally it's good to have a base Cart class so you can better handle and test your operations.
You can then bind that with your GET request:
if (isset($_GET['increase1']))
{
$cart->getItem($_GET['increase1'])->getQuantity->increaseByOne();
}
Some rough Cart and Quantity layout:
Class CartItemQuantity
{
private $item;
private $quantity = 0;
public function __construct(CartItem $item)
{
$this->item = $item;
}
public function increaseByOne()
{
$this->increaseBy(1);
}
public function decreaseByOne()
{
$this->quantity = max(0, $this->quantity - 1);
}
public function increaseBy($number)
{
$this->quantity = max(0, $this->quantity + $number);
}
public function getQuantity()
{
return $this->quantity;
}
public function setQuantity($quantity)
{
if (is_string($quantity) && ctype_digit($quantity))
{
$quantity = (int) $quantity;
}
if (!is_int($quantity))
{
throw new InvalidArgumentException('Not a valid quantity (%s).', $quantity);
}
$this->quantity = max(0, $quantity);
}
}
Class CartItem
{
private $quantity;
...
public function __construct()
{
$this->quantity = new CartItemQuantity($this);
...
}
public function getQuantity()
{
return $this->quantity;
}
}
Class CartItems
{
...
/**
* #return CartItem
*/
public function getItem($item)
{
...
return $item;
}
}
Class Cart
{
/**
* #var CartItems
*/
private $items;
...
public function increaseByOne($item)
{
$this->items->getItem($item)->getQuantity()->increaseByOne();
}
/**
* #return CartItem
*/
public function getItem($item)
{
return $this->items->getItem($item);
}
}

Answer 2

// next line breaks for formatting only, take them out
echo '<form action="cart.php" method="get">
<input type="hidden" name="increasewhat" value="'.$uniquenum.'">
<label for="increaseby">Increase by</label>
<input type="text" name="increaseby" value="1">
<input type="submit" name="increaseyes" value="Yes!">
</form>';
//real linebreaks from here, parameters assumed to be validated
$result = 'cart_' . $_GET['increasewhat'];
$_SESSION[$result] = (isset($_SESSION[$result]) ? $_SESSION[$result]:0)+$_GET['increaseby'];

Answer 3

<form action='cart.php' method='GET'>
Input quantity:<br/>
<input type='text' name='increase1'><br/>
<input type='submit' value='Increase'/>
</form>

Answer 4

<form name="add_to_cart" method="get" action="cart.php">
<label for="uniquenum">Quantity: </label>
<input type="text" name="uniquenum" />
<input type="submit" value="Add to cart" />
</form>
On the server side:
if (isset($_GET['uniquenum'])) {
$uniquenum = $_GET['uniquenum'];
/* Important! Check if it is an integer */
if(is_int($uniquenum)) {
$_SESSION[$result] = isset($_SESSION[$result]) ? $_SESSION[$result] + $uniquenum : 0;
} else {
echo "Invalid input!";
}
}