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How Can I Prevent Unintended Form Resubmission in Web Applications?
- Susan SarandonOriginal
- 2024-11-13 00:43:02618browse
Preventing Unintended Form Resubmission
Form resubmission due to page refresh is a common annoyance in web applications. To handle this issue effectively, it's crucial to employ the following strategies:
Redirect After Submission
Instead of displaying the response on the same page, redirect the user to a separate page once the form is submitted. This ensures that when the refreshed page loads, it's a new GET request and not a repeat of the POST request that has already been processed.
Example:
// submit
// set success flash message (you are using a framework, right?)
header('Location: /path/to/record');
exit;
Disable Browser Caching
To prevent the browser from caching your form, add the following headers to your PHP script:
header('Cache-Control: no-cache, no-store, must-revalidate');
header('Pragma: no-cache');
Unique Page Token
Generate a unique token on the server for each form submission. Include this token as a hidden field in the form and verify it before processing. If the token doesn't match or is missing, discard the request as a duplicate submission.
Example (with session token):
<?php session_start(); // Generate a unique token and store it in the session $token = md5(uniqid(mt_rand(), true)); $_SESSION['token'] = $token; ?> <!DOCTYPE html> <html> <body> <form action="submit.php" method="post"> <input type="text" name="name"> <input type="hidden" name="token" value="<?php echo $token; ?>"> <input type="submit" value="Submit"> </form> </body> </html>
<?php
session_start();
// Get the submitted token
$token = $_POST['token'];
// Check if the token matches the session token
if ($token != $_SESSION['token']) {
// Discard the request
} else {
// Process the form data
}
Conclusion
By implementing these techniques, you can effectively prevent unwanted form resubmissions due to page refresh and ensure that your web application behaves as intended.
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