how do you prevent addition of data when the reresh button is hit

orc

does anyone know how you could prevent the page from adding more data to the database when the user hit the "refresh" button.

sarah

Try getting 'em off the page as soon as the info is added to the database by finishing up with a redirect to a different page? Or...make it so that as soon as the info is added, the same page is refreshed without the submit variable or whatever makes the script put the info in the db?

orc

well, yes, redirecting would be one way. but i'd like to limit myself to redirecting. i had this in my code...but it doesn't work:

if(isset($submit))
{
//code here
}

unset($submit);

sarah

It doesn't work because when the page is refreshed, the code is run again from the beginning, using the original variables...Another idea that might work is to do a query that checks to see if there is an identical entry in the database before the information is inserted. It's one extra step, but it would get the job done.

orc

i am doing a survey input so the data can be repeat.

rpanning

I don't know much about php since I'm kinda new but does anyone think making a session variable would work for this?

orc

session variable would work. But the idea is not to use it since some users disabled their session capabilities.

ahundiak

There is no general solution to the problem. It's part of the fun of programing in a stateless enviroment.

Sarah's idea about checking the database will work in most cases. Each time you build a new form generate and send along (perhaps in a hidden field) a unique string (same concept as a session id). Think of it as a transaction id.

When the data is submitted query a table and see if the transaction id has already been submitted once. If not, add the transaction id to the table and store the rest of your data. If the transaction id has already been posted once then ignore the data.

suntra

Why don't you use sessions ?

You add the session ID in the form, when data is stored in DB, you set a variable, suppose $_SESSION["data_is_submitted"], and you set it to true. But before adding data to your DB, you make sure that variable is set to false... you could also use cookies, but it's not everybody that activates them...

ahundiak

It can be done with sessions but it really would not protect against some things.

Survey 1 is sent to user
data_is_submitted = false.
User submits survey 1 back to server.
data_is_submitted is false so database is updated.
data_is_submitted = true.

So far so good. If survey 1 is resubmitted then the database is not updated.

But, now the user want to vote on survey 2.
Survey 2 is sent to the user.
data_is_submitted = false.

And then the silly user backs up to survey 1 and presses the submit button. Oops.

You really need to track things on a per survey basis if you really want to control the updates.

suntra

Well...

data_for_survey1_is_submitted..
data_for_survey2_is_submitted..

etc... !!!

ahundiak

Yep.

And the posted data knows if it for survey 1 or survey 2. That's the transaction id.

So we have the same design except you are storing the updated flag in a session variable and I stored it in a database table.

orc

i've found a solution to this problem. does anyone wish to see? let me know if you do. i'll post my codings. I had to meditate and sleep over it to figure it out.

ahundiak

orc,
I'd like to see your solution.

orc

Being an ASP developer, I always had the mentality that session variables would not be set when the user disable the feature in her browser. However, with PHP, session variables are stored in two places, the client's and the server's. I've tested my application against the browser being at high security level, which infers that all persistence data and cookies are disabled. My application still worked. So in summary, I had to resolve to using session varialbes, and my solution is simple yet effective than those that are proposed in this thread. Well, here it is:

<?php
session_start();
session_register("submittedId");

if(!isset($submit))
{
$submitId = 1;
$submittedId = 0;
}

if(isset($submit))
{
if($submitId != $submittedId)
{
//codes
$submittedId = $submitId;
$submitId = ($submitId == 0) ? 1 : 0;
}
else
{
$submitId = ($submitId == 0) ? 1 : 0;
}
}
?>

For those of you who do not understand this little coding, let me know so I can comment them.

For those who understand this, let me know if you could come up with a better solution.