sessions/objects

[Anon]

After adding an item to the cart, I hit the back button and my Cart object seems to uninstantiate. I\'ve made this example as concise as I can; please take a look and see if you spot anything dumb. Thanks.

application.php:
<?
require(\"cart.php\");

session_start();
session_register(\"SESSION\");

if (!isset($SESSION)) {
echo \"SESSION: no<br>\n\";
$SESSION = array();
} else {
echo \"SESSION: yes<br>\n\";
}

if (!isset($SESSION[\"cart\"])) {
echo \"SESSION[cart]: no<br>\n\";
$SESSION[\"cart\"] = new Cart;
} else {
echo \"SESSION[cart]: yes<br>\n\";
}
?>

cart.php:
<?
class Cart
{
var $items;

function Cart()
{
$this->init();
}

function init()
{
$this->items = array();
$this->total = 0;
}

function set($id, $q)
{
$this->items[$id] = $q;
}

function add($id)
{
isset($this->items[$id]) ?
$this->items[$id] += 1 :
$this->items[$id] = 1;
}

function display()
{
for ($i=0; $i<10; $i++) {
if (isset($this->items[$i])) {
printf(\"%d=%d<br>\n\", $i, $this->items[$i]);
}
}

echo \"<br>\n\";
}
}
?>

index.php:
<?
include(\"application.php\");
?>

item 1<a href=shopping_cart.php?a=A&id=1>add</a><br>
item 2<a href=shopping_cart.php?a=A&id=2>add</a><br>
item 3<a href=shopping_cart.php?a=A&id=3>add</a><br>

shopping_cart.php
<?
include(\"application.php\");

switch($a) {
case \"A\":
$SESSION[\"cart\"]->add($id);
break;
}

$SESSION[\"cart\"]->display();
?>

[Anon]

I'm not a php pro yet, but I had a similar problem yesterday. It seems that sessions and their variables dont behave the same as regular variables. The session_start(); brings back the values variables had previously, so an unset session var will replace the value posted to the current script when it does it's session_start(); . I had a page which requires $user_id to be set to work normally, and if it is not, it displays a form which instead asks for a user id and posts it to itself (same script). I had to replace:

<?php
session_start();
session_register("user_id");
if(!isset($user_id)) {

With:

<?php
$temp_id = $user_id;
session_start();
session_register("user_id");
if($temp_id != '') $user_id = $temp_id;
if(!isset($user_id)) {

To get it to work...
Also I think your:
session_register(\"SESSION\");
Should be:
session_register("SESSION");
And you may have a few more escaped double quotes too many further down in your script. Remember that you often have to escape double quotes in HTML which is echoed or printed by php but not the other way around...
Just my 2 cents CDN (1.3 US) worth 🙂