What measures can be taken to prevent multiple form submissions in PHP applications?

To prevent multiple form submissions in PHP applications, you can use a token-based approach. Generate a unique token when the form is loaded and store it in a session variable. When the form is submitted, check if the token matches the one stored in the session. If they match, process the form submission; otherwise, reject it. 

session_start();

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    if (!isset($_SESSION['token'])) {
        $_SESSION['token'] = bin2hex(random_bytes(32));
    }

    if ($_POST['token'] === $_SESSION['token']) {
        // Process form submission
        unset($_SESSION['token']); // Remove token to prevent resubmission
    } else {
        // Token mismatch, reject form submission
    }
}
```
In your HTML form, include a hidden input field to store the token:

```html
<form method="post" action="">
    <input type="hidden" name="token" value="<?php echo $_SESSION['token']; ?>">
    <!-- Other form fields -->
    <button type="submit">Submit</button>
</form>

Keywords

Form submission PHP applications Prevent Duplicate submissions CSRF tokens

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