What role does the response play in prompting the browser to remember a redirect, rather than the initial POST request?

When a POST request is made and the server responds with a redirect (HTTP status code 3xx), the browser typically remembers the redirect and automatically sends a GET request to the new location. This can be problematic if you want the browser to remember the initial POST request data and resend it to the new location. To solve this issue, you can use the PRG (Post/Redirect/Get) pattern, where after processing the POST request, you redirect to a new location with a unique identifier in the URL query string. Then, on the new page, you can retrieve the POST data using the unique identifier and process it accordingly.

// Check if form is submitted
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    // Process form data
    // Redirect to new location with unique identifier
    $unique_id = uniqid();
    header("Location: new_page.php?id=$unique_id");
    exit;
}

// On the new_page.php
if ($_SERVER['REQUEST_METHOD'] === 'GET' && isset($_GET['id'])) {
    $unique_id = $_GET['id'];
    // Retrieve POST data using unique identifier
    // Process the data accordingly
}