How can PHP developers prevent old data from persisting when submitting new form data?

When submitting new form data, PHP developers can prevent old data from persisting by using the `unset()` function to clear the values of the form fields after processing the form data. This ensures that the form fields are empty when the page is reloaded, preventing old data from persisting. 

// Process form data
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Handle form submission

    // Unset form fields to prevent old data from persisting
    unset($_POST['field1']);
    unset($_POST['field2']);
    // Add more unset statements for each form field

    // Redirect to prevent form resubmission
    header("Location: ".$_SERVER['PHP_SELF']);
    exit;
}

Keywords

PHP form data data persistence session management data validation

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