Back Button problem aaarrgg!

jorsch

I'm having trouble with the back button on a e-shop:

when i press show_cart.php it show's the items in the shopping cart. at the end of each item is a link to remove that item. the link to remove the item is something like:

removeitem.php?itemnumber

when the link is presses the item is removed and with include(show_cart.php) at the end of the code in the removeitem.php file the cart is showed again.

The problem is when the backbutton is pressed after deleting an item (pressing removeitem.php?itemnumber) the goes to showcart.php. This is no problem cause it shows the cart again and gives the same output. But......when i press forward again..the goed back to removeitem.php?itemnumber and removes another item in the cart which I don't want!

I don't want in any way possible to go back to removeitem.php?itemnumber by using a back button or forward button. I only want this link to be activated when i press the link in the cart.

what should I do?

hope my problem is a bit clear....thanks for the helping out!

trooper

You're probably best off using an existing shopping cart application.

Goto www.oscommerce.com they have a php / mysql one that you can use ans tweak.

I know that i doesn't anwer your question but why try to re-invent the wheel?

ednark

there are always reasons to reinvent the wheel... most shopping carts have a lot of features you personallly are not going to use... and miss a few features you need... and don't integrate well to exactly what you want...

also most carts you can user have this exact smae problem you mentioned...

here is something to think on: you could keep an array in the session...

$SESSION['page_visists_'] = array();

at ever page, push onto this, the page they just requested

array_unshift( $this_page, $SESSION['page_visists_'] );

now $SESSION['page_visists_'][0] always holds the last page they visited... [1] holds the next to last... etc

if you are storing the url_query along with the page name you could check to see if they have previously visited the cart with a query string of REMOVE_ITEM_ID=3, and then simply do not perform that action again.

i don't know if this will really work... but i thought it was worth mentioning

andreiga

I think I had the same problem with my cart.
This is because the url remains in history, so here is something I did.
After you read data from $_GET['itemnumber'] and removed the item from the cart, unset the variable and force a refresh of the page without 'itemnumber'.
This last part you can do it with
header("Location: removeitem.php");
If the headers have been sent already then move the above line after the <body> tag or something (if the output_buffering is set to default(4096) the header will be buffered and sent only after it is filled)

If you still have problems please explain

I hope this helps

jorsch

thanks for the reply

The cart is stored in a session array. The first aticle is stored in ITEM[0], the second as Item[1] and so on. When an item is removed the whole array shifts. Let;s say we have in the cart:

                item-id          amount

item[0] 234 2
item[1] 123 3
item[2] 321 1

when i do remove.php?item=1, item 1 is removed AND the whole array shift one number:

item 1 stays item 1
item 2 is removed
item 3 becomes item 2

                item-id          amount

item[0] 234 2
item[1] 321 1

When i follow your solution i wouldn't be able to remove item 1(that used to be item 2) anymore

still hope there is some sort of simple solution without having to store a new sessionvariable.

jorsch

this is thew remove.php file:

<?
session_start();

for ($i=$item; $i <$cartteller; $i++)
{
$cart[$i]=$cart[$i+1];
}

$cartteller=$cartteller-1;

if($cartteller==0)
{
session_unregister("cart");
session_unregister("cartteller");
UNSET($CART[$cartteller]);
UNSET($cartteller);
echo "cart empty";
exit;
}

header("Location: show_cart.php");

so when i first click showcart.php the fulle cart is shown
then i remove an item with remove.php?tem=2
if the cart has more then one item the cart is updated and shown again with show_cart.php.

when i press back it goes to showcart.php and when i then press forward i go again to remove.php?tem=2

then header thing won't work

ednark

a header must be printed before any other output to the page.. can;t print html, THEN use a header

andreiga

If the header shouldn't work why it is working?
I tested a lot this situation because I really needed a refresh page action
.
So, a little detail. When I used header before any print (e.g. <html>) it didn't work. When I changed every text (even a space or a simple end-of-line as the first character) from pure html to print("html....") and set output_buffering to 4096 from 0 everything worked ok.

I even tested further and pushed header function after a lot of prints (html, body, script etc.) it worked also. But when I pushed the header even further the PHP returned a warning that the headers already have been sent.

I'd like to mention that I execute even the headers_sent
function and everything is behaving like I said before.

If you have any other ideea why this is working please tell me (except the ideea that PHP is buffering data in 4096 bytes and afterwards sends the headers).

ednark

this shouldn't fix everything... but

try
<?php
not
<?

also its best when using the header('Location trick to do it this way

die(header("Location: gohere.php"));

this way you are assured that the very last thing printed before the page kaplups is the location header.

pushed header function after a lot of prints (html, body, script etc.) it worked also

ok here is this

Note: The HTTP status header line will always be the first sent to the client, regardless of the actual header() call beeing the first or not.

are you include()ing any other files or calling any other header() functions before your header("Location") ?

But when I pushed the header even further

i don't understand 'pushed the header even further'. you mean later?

maybe check that there isn't any rogue whitespace before your beginning <? or after your ending ?> for the page...

jorsch

in the code of remove.php the header function is working but does not solve my problem. From remove?item=1 is goes to showcart.php using the header function but the problem still is the back and forward button. a little diagram:

Action: output:

showcart.php cart is displayed
remove?item=1 item removed cart displayed (header)
backbutton showcart.php (same output)
forward button remove?item=1 new item is removed!!

so i don't want remove?item=1 to be recalled...I want it to end up at showcart.php at all times. The browser "remembers" my click on remove.php?item=1

I will try:
<?php

with

die(header("Location: gohere.php"));

as you suggested ednark.....hope it works.

thanks for the replies

jorsch

I changed the file to:

<?php
session_start();

for ($i=$item; $i <$cartteller; $i++)
{
$cart[$i]=$cart[$i+1];

}

$cartteller=$cartteller-1;

if($cartteller==0)
{
session_unregister("cart");
session_unregister("cartteller");
UNSET($CART[$cartteller]);
UNSET($cartteller);
die(header("Location: show_cart.php"));
}

die(header("Location: show_cart.php"));

it doesn't work for my problem. still when i press the back button i go to showcart.php and when i press the forward i go to remove.php?1

sorry.....any other suggestions anyone?