What potential issues can arise when using the POST method in PHP forms, specifically with Internet Explorer 9?

When using the POST method in PHP forms, specifically with Internet Explorer 9, a potential issue that can arise is that the browser may cache the form data and resubmit it when the user navigates back to the page. This can lead to duplicate form submissions and other unintended consequences. To prevent this, you can use the PRG (Post-Redirect-Get) pattern, which involves redirecting the user to a different page after processing the form data.

// Check if form is submitted
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Process form data
    
    // Redirect to a different page to prevent form resubmission
    header("Location: success.php");
    exit;
}