What are the best practices for preventing multiple form submissions in PHP?

To prevent multiple form submissions in PHP, one common approach is to use a token-based method. This involves generating a unique token when the form is loaded and storing it in a session or hidden form field. When the form is submitted, the token is validated to ensure that the form is only processed once. 

<?php
session_start();

if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    if (isset($_POST['token']) && $_POST['token'] == $_SESSION['token']) {
        // Process the form submission
        // ...
        
        // Unset the token to prevent multiple submissions
        unset($_SESSION['token']);
    }
}

// Generate a unique token and store it in the session
$token = md5(uniqid(rand(), true));
$_SESSION['token'] = $token;
?>

<form method="post">
    <input type="hidden" name="token" value="<?php echo $token; ?>">
    <!-- Other form fields -->
    <button type="submit">Submit</button>
</form>

Keywords

form submissions prevent duplicate token session

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