[Resolved] Problem with Objects and Sessions

[davidjam]

Hello,

First time on PHPBuilder. Looks good so far. I am about 1 year into learning PHP.

I am just starting out on PHP4-OOP. Here is my problem:

Page 1

include "class.inc"
// "class.inc" has a class called page and in that class a constructor that defines $msg = "hello"
session_start()
$page = new page
$_SESSION['object'] = $page;
// I have also tried session_register($page)

Page 2

include "class.inc"
session_start()

print $page->msg

I get no result here (i.e. "hello"). Why can't I access my object??

[drawmack]

you have not defined $page in page 2. Try at the top of your script doing error_report('E_ALL'); that will give you notices about this type of thing.

[davidjam]

But I don't want to instantiate the object again, I just want to access one of its variables or manipulate the object (i.e. by changing a variable or whatever) on other pages.

[drawmack]

you must instantiate the object on every page you wish to use it on, in order to use it like you're trying to.

[davidjam]

OK I instantiated the object on the second page. But here is the revised scenario so that you can see what I am trying to do:

class.inc (revised)

var $eraseme
function eraseme() {$this->eraseme = "the message"}

page 1

include "class.inc"
session_start()
$page = new page
$page->eraseme() <--- sorry I forgot to include this on the last post
$_SESSION['object'] = $page

print $page->eraseme

// result: "the message"

page 2

include "class.inc"
session_start()
$page = new page

print $page->eraseme

// NO RESULT

why?

[drawmack]

class.inc (revised)

<?php
class page {
    var $eraseme
    function eraseme() {$this->eraseme = "the message"}
}
?>

page 1

<?php
include "class.inc"
session_start()
$page = new page();
$page->eraseme() 
$_SESSION['object'] = $page

print $page->eraseme
?>

// result: "the message"

page 2

<?php
include "class.inc"
session_start()
$page = new page();
//you're not calling eraseme, this is a new instantiation.
print $page->eraseme;
?>

// NO RESULT

[davidjam]

You told me I had to instantiate the object on every page.

What's the point of objects if they can't travel from one page to the next and CARRY THE VARIABLES WITH THEM. For instance, if function eraseme had an argument, i.e.:

function eraseme($message="default message") {$this->eraseme = $message}

and on page 1 I set the message:

$page->eraseme("this is the message I want to stick!") // i.e. not the default message

does that mean that on page 2 I have to set it again? That seems rather pointless, unless, for instance, I wanted to change the message, in which case it makes sense.

Sorry for the frustration. Maybe my expectations are too high. Thanks for your replies.

[davidjam]

I guess what I wanted to emphasize in that last post was:

Does that mean I have to set the variable again on every other page?

If that is true, I might as well go back to using the session array for every variable I want to "stick", but then I lose all the advantages of objects...

[drawmack]

http://www.php.net/serialize
http://www.php.net/unserialize

The main point of objects is portability. Everytime the browser loads a new page it is a new program running. The program will not remember what was done in a previous program, or even a previous instance of the same program. The equivalent in desktop computing would be closing the progeam and starting it again, you'd have to resetup all your classes at that point too.

[davidjam]

I noticed you provided links to the serialize and unserialize functions. I will check them out before I say anything else. Thanks for the help.

[davidjam]

1. OK I just came back from checking out the two links. The implication is that serializing and unserializing with session objects is automatic. Is that true?

2. Following up on my example. Here is the print_r of the session on page 2:

Array ( [object] => page Object ( [eraseme] => the message I want to persist ) )

So why can't I get that custom value (the eraseme message) to "reload" into the object on page two. I mean isn't that how shopping carts work: the $cart "remembers" the items no matter what page the user is on???

[davidjam]

The problem was so simple it is almost embarassing. Essentially it boils down to this:

Session objects (that is objects that persist page to page for a particular user) must be instantiated, variables changed, functions called and otherwise manipulated as a KEY OF THE SESSION SUPERGLOBAL ARRAY.

So I just changed this:

$page = new page();

To:

$_SESSION['page'] = new page();

And of course any other object manipulation, for instance:

$_SESSION['page']->eraseme("the message I want to persist")

Which is easily called on page 2 via:

$_SESSION['page']->eraseme

Voila

Thanks so much.