Refresh page without changing anything in the page

wendyz · #1 23-Feb-2009, 15:46

I write HTML and use 'form' to post data to next page. In next page, I $_POST[] data and store into database, it should be done for this process. But if I click "refresh button", the data will be posted from last page again, and also store the data into database, that will duplicate data, which is not what I want. so How can I do? Any good idea.

Blake · #2 23-Feb-2009, 16:57

I usually handle that situation by keeping a session variable, formID, which increments every time a form is submitted. Every form also has a hidden formID input. When the form is submitted, the php script that processes the form data checks if the formID value from the form matches the session variable. This works because when you refresh a form, the hidden formID that is reposted no longer matches the session variable, since the session variable would have been incremented the first time the form was submitted.

Here's a simple example. In your HTML form:

HTML Code:


<input type="hidden" name="formID" value="<?= $_SESSION['formID'] ?>">

And in the php script that processes the form:

PHP Code:


if ($_SESSION['formID'] != $_POST['formID'])
{
  echo "You refreshed your browser fool!";
}
else
{
  $_SESSION['formID']++;
  // process form
}

You'll need to initialize the value of the session variable somewhere, probably when you initialize the session.

wendyz · #3 24-Feb-2009, 17:00

thanks! works

Blake · #4 24-Feb-2009, 17:08

You're welcome.

MisterChucker · #5 29-Mar-2009, 17:30

Another solution is to use an intermediate script, as in the following example. The intermediate script is virtually invisible to the user, who can use Refresh and Back buttons without consequence.

form.php

HTML Code:

<html>
<head>
<title>Example Input Page</title>
</head>
<body>

<h2>Input Page</h2>

<form action="validate.php" method="post">
	<input type="submit" name="btnSubmit" value="Save current time to file" />
</form>

<pre>$_POST =&gt; <?php print_r($_POST); ?></pre>

</body>
</html>

validate.php

PHP Code:


<?php
if (isset($_POST['btnSubmit']))
{
    // Confirms that this script ran by writing the current time to a file
    file_put_contents('current_time.txt', date('Y-m-d H:i:s'));
    
    /*
     * If there are variables you want to use in confirm.php, you need to store
     * them in $_SESSION because the scope of variables is limited to
     * validate.php unless you use a require or include.
     * 
     * Remember to not echo or print anything in validate.php or you will get a
     * "headers already sent" error.
     */
    
    // Redirects to a confirmation page
    header('Location: confirm.php');
    
    /*
     * Meanwhile, the script continues. You could also put code after header().
     * 
     * One problem with this method is that no variables modified from here to
     * the end of validate.php can affect what is shown on confirm.php, even if
     * you store them in $_SESSION.
     */
}
?>

confirm.php

PHP Code:


<html>
<head>
<title>Example Confirmation Page</title>
</head>
<body>

<h2>Confirmation Page</h2>

<p>$_POST should be an empty array:</p>

<pre>$_POST =&gt; <?php print_r($_POST); ?></pre>

<p>Current time: <?php echo date('Y-m-d H:i:s'); ?></p>

<p>Try using your Refresh or Back button. Compare the current time on this page
to the time stored in current_time.txt:</p>

<pre><?php echo file_get_contents('current_time.txt'); ?></pre>

</body>
</html>

current_time.txt

Code:

2009-03-29 16:16:21

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Refresh page without changing anything in the page

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