Session variable not saved

Muad_Dib

I have a complicated script containing a problem with a destroyed session variable (through the $_SESSION array) which reappears on the next page.

Here is a small script with the same behaviour :

=======================
<?php
ob_start() ;
?>
<html>
<body>
<?php
// Useful function
function dumpArray($Tablo)
{
$Entete = date("H:i:s - ") ;
while (list ($Cle, $Valeur) = each ($Tablo))
echo ($Entete . $Arguments[$i] . '[ ' . $Cle . ' ] = ' . $Valeur . "<br/>\n") ;
}

// Beginning of session variables usage
session_start();

dumpArray($_SESSION) ;

if (isset($SESSION['Foo_2']))
unset($SESSION['Foo_2']) ;
else
if (isset($SESSION['Foo_1']))
$SESSION['Foo_2'] = 'blue' ;

$SESSION['Foo_3'] = 'yellow' ;
$SESSION['Foo_1'] = 'red' ;
unset($_SESSION['Foo_3']) ;
?>
<a href="#" onclick="window.location.href='session_test.php';"><b>Next call</b></a>
<br>
</body>
</html>
<?php

dumpArray($_SESSION) ;

// session_write_close() ;
ob_end_flush() ;

// Should be :
// First call : Foo_1 defined
// Second call : Foo_1 and Foo_2 defined
// Next odd call : Foo_1 defined
// Next even call : Foo_1 and Foo_2 defined
//
// Is :
// First call : Foo_1 defined
// Second call : Foo_1 and Foo_2 defined
// Other calls : Foo_1 and Foo_2 defined
//
// session_write_close() ; // doesn't change anything

?>

Just copy this script in a file named 'session_test.php' and lauch it then click on the 'next call' link several times.
(have also attached the script as a zip file)

Should be something obvious I don't see...
Or maybe the ob_xxx functions interfere (but I need them in my true script).
Works same under Windows/IIS and Linux/Apache.

Any idea ?

Thanks.

Weedpacket

Works for me (written in the from below; I took out dumparray because it's a bit buggy). Before PHP (I forget which version) unset($SESSION['foo']) wouldn't work properly - it would unset the value in the $SESSION array, but it wouldn't actually remove it from the session data. The workaround was $_SESSION['foo']=null;

<?php
ob_start() ;
?>
<html>
<body>
<?php


// Beginning of session variables usage
session_start();

var_dump($_SESSION) ;

if (isset($_SESSION['Foo_2']))
unset($_SESSION['Foo_2']) ;
else
if (isset($_SESSION['Foo_1']))
$_SESSION['Foo_2'] = 'blue' ;

$_SESSION['Foo_3'] = 'yellow' ;
$_SESSION['Foo_1'] = 'red' ;
unset($_SESSION['Foo_3']) ;
?>
<a href="sc.php"><b>Next call</b></a>
<br>
</body>
</html>
<?php

var_dump($_SESSION) ;

// session_write_close() ;
ob_end_flush() ;

// Should be :
// First call : Foo_1 defined
// Second call : Foo_1 and Foo_2 defined
// Next odd call : Foo_1 defined
// Next even call : Foo_1 and Foo_2 defined
//
// Is :
// First call : Foo_1 defined
// Second call : Foo_1 and Foo_2 defined
// Other calls : Foo_1 and Foo_2 defined
//
// session_write_close() ; // doesn't change anything
?>

Muad_Dib

Your version doesn't work on my two systems (Windows and Linux), too.

Begining at the third click on 'Next call', values remain always the same (Foo_1 and Foo_2 always reloaded with their previous value at session_start).

The problem should not be with 'unset' (Foo_3 is well destroyed and when dumped after the 'unset', $_SESSION doesn't contain Foo_2. So, it should not be saved in the session file at the end of the script).

But, following your comment, I have also tried with '=null' instead of 'unset' and it has a strange effect :
Foo_2 remains always defined (when dumped), but one time it contains 'blue' and one time it contains 'null' (and with this value, 'isset' returns false).
Maybe it is a workaround, but not satisfactory.

Thanks.

PS : I don't understand where my 'dumpArray' function is buggy (it has always worked fine for me - when the argument was an array).

Weedpacket

The code I posted was exactly yours, with var_dump instead of dumparray().

So, ah, which version are you using, then? The behaviour you describe with "unset" is correct, but the problem was that even though Foo_2 was no longer in the $_SESSION array, it was still being written out to the session file.

PS : I don't understand where my 'dumpArray' function is buggy (it has always worked fine for me - when the argument was an array).

Oh, it's just that it would have thrown loads of notices about $Argument and $i not being declared is all 🙂. I just prefer var_dump() anyway (even preferring it over print_r()) because it provides more information (and works on any variable).

Muad_Dib

Yes, I have changed the session handling functions in order to try to see what happens and the Foo_2 variable is always written in the session file though it is no more present in the $_SESSION array.
Seems to me like a bug, no ? Or is it just an 'undocumented feature' ???

I use PHP version 4.2.3 on my local Windows and version 4.1.2 on the hosted Linux.
The behaviour is exactly the same with the two versions.

minorgod

You might calling session_start() before you start ouputting any HTML code. This will also keep you from needing the output buffering so you can lose the ob_start and ob_end_flush calls as long as you're not outputting any characters to the browser before you make your session modifications. You should try to keep all your PHP logic above the HTML code and just use php within the html to display data, not to perform operations. This will keep you from needing output buffering in most cases.