Stop a posted form from re-posting

Question

I need to be able to stop a page from posting once the data in it has been submitted. For example I could have this form:

<form action='#' method='post'>
    <input type='text' name='name' />
    <input type='submit' name='submit' />
</form>

Then catch the post like this:

<?php
if (isset($_POST['submit'])) {
    echo "Hello " .  $_POST['name'];
}
?>

But when the page refreshes it will preform the same action time and again until either the user leaves the page or does a full refresh on the page. This is causing me a huge issue as it is imperative I am able to stop the post from preforming once it has been done.

I have tried using a meta tag (<meta http-equiv="refresh" content="5">) to refresh the page, but this caused an issue as every few seconds it would do it and the page data was lost, I have tried to unset the post variable (unset($_POST['submit']); and unset($_POST);), but this did not work, I cannot use header("Location: ...") as I am using WordPress and thus headers are always sent by the system.

So I ask this of the community we have: How can I stop the post from re-submitting the data?

EDIT

What I am now doing:

<?php
if (!isset($_SESSION)) {
    session_start();
}
$token = rand();
if ($_POST) {
    if (isset($_SERVER['token'])) {
        if($_POST['token'] == $_SESSION['token']){
            $continue = FALSE;
        }
        else {
            $continue = TRUE;
        }
    }
    else {
        $_SERVER['token'] = $_POST['token'];
        $continue = TRUE;
    }

    if ($continue === TRUE) {
        if (isset($_POST['update'])) {
            //Do update code
        }
        if (isset($_POST['win'])) {
            //Do win code
        }
        if (isset($_POST['credit'])) {
            //do credit code
        }
    }
}

Form:

<form method="post" action="#">
    <select name="select">
        <option value="false" <? if ($results->data[$i]['marked'] == "false") { echo "selected"; } ?>>No Attention</option>
        <option value="true" <? if ($results->data[$i]['marked'] == "true") { echo "selected"; } ?>>Needs attention</option>
    </select>
    <input type="hidden" name="token" value="<?php echo $token; ?>" />

    <input type="hidden" name="betid" value="<? echo $results->data[$i]['bet_id']; ?>" />
    <input name="update" id="" class="btn btn-default" value="Update" type="submit">
</form>

Answer 1

You can do it like this:

<?php
$token = rand(); //Or how ever you want to generate a random token
?>

<form action='#' method='post'>
    <input type='text' name='name' />
    <input type="hidden" name="token" value="<?php echo $token; ?>" />
    <input type='submit' name='submit' />
</form>

Then catching the post

<?php
if(isset($_POST['submit'])){
   if (isset($_SESSION['token']) ) {
       if($_POST['token'] == $_SESSION['token']){
           $continue = FALSE;
       }else{
           $continue = TRUE;
       }
   }else{
     $continue = TRUE;
   }

  if($continue === TRUE){
     $_SESSION['token'] = $_POST['token'];
     //DO SOMETHING
  }
}
?>

It can properly be made smaller / more compact but you should get the idea behind the code, this way if a user who has already submitted data can submit new data if he access the form a new, but if the page refreshes the data won't be procesed again

Of course you have to be sure that SESSION is startet

Answer 2

This is a perfect question to link one of my favourite answers on Stackexchange: https://softwareengineering.stackexchange.com/questions/46716/what-technical-details-should-a-programmer-of-a-web-application-consider-before

This answer also says:

Redirect after a POST if that POST was successful, to prevent a refresh from submitting again.

I do recommend you to click on the link.

So basically to redirect after a post has been submitted. Instead of posting to the page you go to now when you post information, you post to a redirect that redirects to the page you want to go. This will make sure when you refresh, it wont post the information again.