asked on

SESSION values incorrect after POST / refresh

I am trying to save a value to a session variable and use it later for verification purposes, but this value is updated / altered by php if the user waits too long before reloading the page.

An example with code follows. In this example, I simply want the SESSION variable to update by a count of 1 everytime the page is loaded or reloaded. Unfortunately, if you wait 5, 10, 15 or more seconds and then hit refresh, the counter increases by a much larger factor. I do not understand what is happening, and why php is arbitrarily changing my SESSION values.

The same happens when I store the current time. PHP will change the time on the next refresh.

I am using PHP 4.3.10. I am not sure if there were known SESSION issues with this load.

code:

<?

session_start();

// Check if variable is set. If so, print it.. if not, say so.
 echo "START ";
 if (isset($_SESSION['dCode']))
 echo "SESSION dCode = " . $_SESSION['dCode'] . " ";
 else
 echo "SESSION dCode not SET ";
 echo " ------------------------ ";

// Retrieve Session Variable contents
 if (isset($_SESSION['dCode']))
 $temp = $_SESSION['dCode'];
 else
 $temp = 0;

// Update Variable here
 $_SESSION['dCode'] = $temp + 1;

// This should show the incremented variable.
 echo "END ";
 if (isset($_SESSION['dCode']))
 echo "SESSION dCode = " . $_SESSION['dCode'] . " ";
 else
 echo "SESSION dCode not SET ";
 echo " ------------------------ ";

?>

Roonaan

How would php know that you don't want to change the variables on refresh?

-r-

Ivo Stoykov

Hello Skytzo,

> The same happens when I store the current time. PHP will change the
> time on the next refresh.
this is normal because each refresh is a new different request/response communication between client and server. If your logic is to increment the value each time the page is hit - php just does this.

you could try to implement some logic to diferenciate requests by client's IP or cookies or whatever else and to increment the value only of these are diferent values...

HTH

I

Skytzo

ASKER

Let me explain a little more why I am puzzled by this.

If I load the page and get the counters to show

1
2

I am fine, since they are sequential and correct. When I refresh the page, I would expect the counters to show

2
3

BUT, this is not always the case. If you wait 10 seconds or so and hit refresh, you could see something like

14
16

I would like to know where PHP gets the arbitrary value to increase my counters? It is as if it assumes I have reloaded the page multiple times when I have only done it once.

Ivo Stoykov

Hi Skytzo,

check where else you're using $temp variable...

regards

I

Skytzo

ASKER

In this case no where.. That is why I wanted to give you all a simple single page code example to try out yourselves. Here it is, even simpler. Excuse the lack of error handling code.

Put this code in a php file and run it yourself. Refresh the page a couple of times. Then wait some time between refreshes. You will see that the SESSION value is only updated after the initial echo statement, yet when you refresh, somehow, the SESSION value is modified from when it was last displayed.

The first echo should be the same as the last echo prior to refreshing the page. Does that make sense?

<?

session_start();

echo $_SESSION['value'];

// Update Variable here
$_SESSION['value'] = date("H:i:s");

echo $_SESSION['value'];

?>

Ivo Stoykov

Hi Skytzo,

<?

session_start();

echo "old value: " . $_SESSION['value'] . " ";

// Update Variable here
$_SESSION['value'] = date("H:i:s");

echo "new value: " . $_SESSION['value'];

?>

the result at mine machine is

old value: 10:26:18
new value: 10:26:49

old value: 10:26:49
new value: 10:27:03

i.e. only seconds have changed which correspond to the interval between reloads...

regards

I

dutchclan

as ivostoykov stated it should not be any problem.

But you might want to try writing them to vars and process the increase there and rewrite them to the session vars.

Something like

<?php

If(isset($_SESSION['dCode']) ){
$my_var = $_SESSION['dCode'];
unset($_SESSION['dCode']);
$my_var ++;
$_SESSION['dCode'] = $my_var;
}else{
$my_var = 1;
}

echo "$my_var";

?>

This way you are sure you always calc with empty array`s (my_var is reset on reload) and always sure you work with an emty $_SESSION for its unset then set again. This way you will get a better fault tollerance.

Good luck

dutchclan

Ps!!

do unset($_SESSION['my_val']); before writing to it, always make sure the array key is empty before you write the new value.

ClickCentric

For the record, your original code works just fine for me on my server. I have php 4.4.2. You may want to check your session settings. Though that doesn't seem too likely either. You don't have more than one browser window open to that page when you're testing it, do you? You may be overlapping your sessions.

Skytzo

ASKER

Alright.

I am using IE 7 beta 2 and it appears that this is causing the problem with php sessions. Firefox worked correctly.

I will have to get IE 6 going again.

Thanks.

ClickCentric

Thanks for the points, though I didn't really answer your question. But a C?? :P Seriously, though, I wouldn't mind if you wanted to have the points recalled and just close the question.

Skytzo

ASKER

That suits me. How do I go about getting points recalled?

C, because of the way they worded the A, B and C. Its not meant as a hit or anything. I will see what I can do.

ClickCentric

I think you can just post a message in the support section. I've never actually done it, though, so don't quote me on that.

ASKER CERTIFIED SOLUTION

Netminder

membership

This solution is only available to members.

To access this solution, you must be a member of Experts Exchange.

Start Free Trial