Basic objects help please

cusimar9

I'm fairly new to PHP and I'm trying to build a small shopping cart class and it seems I'm falling over at the first hurdle 😕

I have 2 classes, the intention being that I have a 'Shopping Cart' which contains a list of 'Products'.

class Product {
    public $productid, $name, $qty, $price;

public function __construct($iProductID, $iName, $iQty, $iPrice) {
    $this->productid = $iProductID;
    $this->name = $iName;
    $this->qty = $iQty;
    $this->price = $iPrice;                                
}   

public function value() {                       
      return $this->price * $this->qty;
}     
}

class ShoppingCart {

public $products;

function add_product($product_id, $qty) {
    $result = mysql_query("SELECT * FROM products WHERE productid = ".SQL::quote($product_id));
    if ($row = mysql_fetch_array($result,MYSQL_ASSOC)) {
        $this->products[] = New Product($product_id, $row['title'], $qty, $row['price']);
    }
} 

function remove_product($product_id) {
    foreach ($this->products as $key => $product) {
     	if ($product->productid == $product_id) {
     		unset($this->products[$key]);
     	}
     }
}

public function cartValue() {
    $total = 0;

    foreach ($this->products as &$product) {  
        $total += $product->value();
    } 
    return $total;
}  

} // end of class

and I'm using it as follows:

    $cart = $_SESSION['CART'];
    if (!isset($cart)) $cart = new ShoppingCart();

$cart->add_product(1,2);

//$cart->remove_product(1);


foreach ($cart->products as &$product) {   
    echo($product->productid . "<br />");
    echo($product->name . "<br />");
    echo($product->price . "<br />");
    echo($product->qty . "<br />");
    echo($product->value() . "<br /><br />");
}

echo $cart->cartValue();

$_SESSION['CART'] = $cart;

The shopping cart needs to be saved and retrieved from the session.

I've been testing it by 'adding' and 'removing' products, and even the add doesn't seem to work.

If I blank the session, and run the script once, it should add 1 product, and print it to the screen. It does this.

If I then comment out the add product line, and run the script again I expect it to load the shopping cart from the session and just print out the one product that's already been added. Instead, it prints out two copies of the same product.

There's a problem somewhere when storing it to the session because it seems to be making two copies of every product.

This is what is shown on the second refresh (I have commented out the 'add' at this point)

1
6x4 picture
2.99
2
5.98

1
6x4 picture
2.99
2
5.98

11.96

Like I said I'm pretty new at this so any advice and any pointers would be much appreciated.

NogDog

I could not reproduce your problem. I copied-and-pasted your code, but I did have to change it to bypass the database stuff. This is what I used:

<?php
class Product
{
   public $productid, $name, $qty, $price;

   public function __construct($iProductID, $iName, $iQty, $iPrice)
   {
      $this->productid = $iProductID;
      $this->name = $iName;
      $this->qty = $iQty;
      $this->price = $iPrice;
   }

   public function value()
   {
      return $this->price * $this->qty;
   }
}

class ShoppingCart
{

   public $products;

   function add_product($product_id, $qty)
   {
      /*
      $result = mysql_query("SELECT * FROM products WHERE productid = " . SQL::
         quote($product_id));
      if ($row = mysql_fetch_array($result, MYSQL_ASSOC))
      {
         $this->products[] = new Product($product_id, $row['title'], $qty, $row['price']);
      }
      */
      $this->products[] = new Product(rand(1,99), 'title'.rand(1,99), rand(1,10), rand(1,999)/100);
   }

   function remove_product($product_id)
   {
      foreach ($this->products as $key => $product)
      {
         if ($product->productid == $product_id)
         {
            unset($this->products[$key]);
         }
      }
   }

   public function cartValue()
   {
      $total = 0;

  foreach ($this->products as & $product)
  {
     $total += $product->value();
  }
  return $total;
   }

} // end of class

session_start();
$cart = $_SESSION['CART'];
if (!isset($cart))
   $cart = new ShoppingCart();

$cart->add_product(1, 2);

//$cart->remove_product(62);

foreach ($cart->products as & $product)
{
   echo ($product->productid . "<br />");
   echo ($product->name . "<br />");
   echo ($product->price . "<br />");
   echo ($product->qty . "<br />");
   echo ($product->value() . "<br /><br />");
}

echo $cart->cartValue();

$_SESSION['CART'] = $cart;

cusimar9

Oh my GOD you won't believe what it was. This is brilliant.

Your version above worked great (thanks a lot for the help 🙂 ) so I cannibalised my page until it resembled yours in the hope that, eventually, it would work.

So firstly I removed all my include files, then all the DB connection, then ALL other PHP code from the page, still no difference.

I then started to remove HTML from the page and it suddenly worked (?)

Eventually I'm going through the HTML LINE BY LINE to try and find what's causing it... and you'll never guess what it was:

<img id="big_porfolio_picture" src="" alt="" />

A bloody image with no source (its set by javascript at runtime). The browser was taking the empty src attribute and taking it to mean TRY AND LOAD THE CURRENT PAGE! So for every page load, it was trying to do two.

Un-believable. What a great way to waste 3 hours.

NogDog

Heh, I would never have guessed that unless I got to it by process of elimination like you did. Thanks for following up in case anyone ever runs into that, too.

Now if I can only think of a way to use that as a feature in something... :rolleyes: