What is the common issue with form content disappearing when using the back button in PHP?

When using the back button in a browser after submitting a form in PHP, the form content may disappear because the browser caches the previous page without the form data. To solve this issue, you can use the POST/Redirect/GET design pattern. After processing the form data, redirect the user to another page using the header() function to prevent resubmission of the form data when the user navigates back.

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

    // Redirect to another page
    header("Location: success.php");
    exit;
}