help with a coding problem regarding sessions and register_globals being off

filch

Hello,

I am relatively new to PHP but I am learning fast. I still have a long way to go. And, I apologize for the length of this thread.

I took on the task of building a shopping cart partially because I needed one for a demo and I thought it would be a great way to learn. With some starts and stops, I have been managing to get thru a lot of it. However, I am at the actual cart portion of this application and I am finding myself stumped or at least stalled. Perhaps a fresh set of eyes on my problem can help me out. Essentially, I have this piece of code that is supposed to take input from an 'Add To Cart' button on a catalog page and if a cart is empty or does not exist, the globals $cart, $item, $item_price are registered with the session. The product sku number is sent to this script like so when the 'Add To Cart' is clicked: cart.php?new=20030001. So my code is as follows: [register_globals = off]

<?php
session_start();
include('assets/includes/pc01_store_fns.php');

//do_html_header('Your Shopping Cart');

if($GET['new'])
{
$new=$GET['new'];

//new item selected
if(!session_is_registered("cart"))
{
  session_register("cart");
  $cart = array();

  $items = 0;	  
  session_register("items");
  $total_price = "0.00";
  session_register("total_price");
  $sessionId = session_id();
}

 $cart=$HTTP_SESSION_VARS['cart'];
 if($cart[$new])
    $cart[$new]++;
 else
    $cart[$new] = 1;

$total_price = calculate_price($cart);
$items = calculate_items($cart);

}

if($save)
{
foreach ($cart as $itemSku => $qty)
{
if($$itemSku=="0")
unset($cart[$itemSku]);
else
$cart[$itemSku] = $$itemSku;
}
$total_price = calculate_price($cart);
$items = calculate_items($cart);
}

The theory here is that if the item is already in the cart ;

if($cart[$new])
$cart[$new]++;

then the quantity is adjusted up by a unit of 1. If it is not in the cart;

else
$cart[$new] = 1;

then it is added with a quatity of 1. What is actually happening is:

if I add say the first item in a category, it adds to the cart and displays fine with the proper quantity. If I 'Continue Shopping' and add the same item again, it updates the cart and now shows a quantity of 2. This is correct. If, however, I do it again .. the quantity remains unchanged. It is not a display code error as I check the ontents of the $cart array and it has not been updated. I do not get this.

Then if I add say the second item on the category page at this point, it adds a second item to the cart and displays it fine with a quantity of 1 but it changes the quantity of the first item added to the cart back to 1.

Here is my calculate_items code which is in an include file:

<?php

session_start();

function calculate_items($cart)
{
// sum total items in shopping cart
$items = 0;
if(is_array($cart))
{
foreach($cart as $items => $qty)
{

$items += $qty;
}
}
return $items;
}

I know this is going to be a stupid rookie coding mistake but I have been too close to this for too long and I am not seeing it so if someone out there can take the time to help an amateur out here ... I would sincerely appreciate it.

Cheers

Dave

filch

I am not sure if I am on the right track here but I was just trying to figure out what is going on with session control and using it under a server with PHP register_globals off. So I was going thru this simple example of sessions I found on the WebDev site. I.E.

I created a simple page with this code in it:

<?
session_start();
session_register("SESSION");

if (! isset($SESSION)) {
$SESSION["count"] = 0;
echo "<li>Counter initialized, please reload this page to see it increment";
} else {
echo "<li>Waking up session $PHPSESSID";
$SESSION["count"]++;
}
echo "<li>The counter is now $SESSION[count] ";
?>

When I tested this page it would not work. The counter never incremented etc. etc. So, I figured, well, it must be because of the register_globals off thing. I modified the code to this:

if (! isset($HTTP_SESSION_VARS['SESSION'])) {
$SESSION["count"] = 0;
echo "<li>Counter initialized, please reload this page to see it increment";
} else {
echo "<li>Waking up session $HTTP_SESSION_VARS[$PHPSESSID]";
$SESSION["count"]++;
}
echo "<li>The counter is now $SESSION[count] ";

Now it will increment to 1 but no farther. What's up with that? Do I have to use something like $_SESSION["SESSION"[count]]++; I am obviously having trouble with the proper sytax to use here with reister_globals off. Also, PHP will parse this file ?BU?T if gives me undefined variable errors for $PHPSESSIONID and undefined index errors for count. I need some straightening out here. Anyone?

Dave

nnichols

Try this as a test -

<?php 
session_start(); 
// Use $HTTP_SESSION_VARS with PHP < 4.1
if ( !isset( $_SESSION['count'] ) ) 
{ 
$_SESSION['count'] = 0; 
echo $_SESSION['count']; 
} 
else 
{ 
$_SESSION['count']++; 
echo $_SESSION['count']; 
} 
?>

filch

OK .. so that works. I assume you would still have to session_register("SESSION") ???

Or, am I confused here? Let's say I needed to register 'SESSION' and do so by issuing session_register("SESSION"); It should now be available as $SESSION .. yes?
So now, assigning a value to this with $SESSION['count'] = 0; is correct ... yes? So incrementing this with $SESSION['count']++; would also be correct .. would it not? So why doesn't my first example work?

Or .. do you no longer have to specifically register sessions? Is it done automatically with the code: $_SESSION['count'] = 0;

And how would I output the the session id? ($PHPSESSIONID)

I am sorry .. I feel a bit silly but I seem to be missing something critical here.

Thanks ..

Dave

nnichols

Using the "session_register()" function just adds the variable to the $_SESSION array. So the following are equivalent -

$var = 0;
session_register('var');

$_SESSION['var'] = 0;

You need to call "start_session()" before accessing the session vars, but if you use 'session_register()' or any other 'session_**()' function it will automatically start the session, though it is good practice to call 'session_start()' in the code first.

If you have globals on then any session var will be availbale as $var but with globals off you need to access it via the $_SESSION array.

To output the SESSIONID you can use -
echo SID;

but this will not be set if PHP has managed to set the session_cookie and you will have to access the session id with "$PHPSESSID"

SID is the constant defined automatically by PHP when it fails to access/set the session_cookie.

It is worth having a thorough read of the manual.

Hope this helps 😉