Randomized thank you page redirect with unique slug

gistfile1.txt

Copy the following PHP code and create a PHP snippet using your snippet plugins. 
Paste the code into the plugin and save it.

Changes page ids: function add_specific_rewrite_rule_for_thank_you_page() {
    // Get the post ID for your thank-you page
    $thank_you_page_id = YOUR PAGE ID;
    
and: function handle_thank_you_page_redirection() {
    // Define the post ID for your thank-you page
    $thank_you_page_id = YOUR PAGE ID;


Description
Above code snippet handles a redirect to a thank you page in WordPress by creating a unique slug every time and securing 
it with a nonce. On form submit, a user will be redirected to a dynamically created URL that may possess some sort of unique 
identifier. If the same URL is tried to visit again by the user, he will be rerouted to the home page. The implementation uses 
transients in tracking visits and nonces to prevent some unauthorized requests.

_______________________________-

add_action('template_redirect', 'handle_thank_you_page_redirection');

function handle_thank_you_page_redirection() {
    $thank_you_page_id = YOUR PAGE ID;

    // Allow editors/admin/preview
    if (is_admin() || isset($_GET['elementor-preview']) || isset($_GET['bricks'])) {
        return;
    }

    if (is_page($thank_you_page_id)) {

        //  Dynamically check if ANY query string (besides unique/nonce) exists = must be from form
        $query = $_GET;
        unset($query['unique'], $query['nonce']); // ignore system keys

        // If no other query arguments = probably accessed manually → redirect to homepage
        if (empty($query)) {
            wp_safe_redirect(home_url(), 302);
            exit;
        }

        // If unique/nonce missing or invalid → redirect with same query args + new nonce
        if (!isset($_GET['unique']) || empty($_GET['unique']) || !isset($_GET['nonce']) || !wp_verify_nonce($_GET['nonce'], 'thank_you_nonce')) {
            $unique_slug = bin2hex(random_bytes(8));
            $nonce       = wp_create_nonce('thank_you_nonce');

            $query_args = $_GET;
            $query_args['unique'] = $unique_slug;
            $query_args['nonce']  = $nonce;

            $new_url = add_query_arg($query_args, get_permalink($thank_you_page_id));
            wp_safe_redirect($new_url, 302);
            exit;
        } else {
            // Prevent revisit
            $unique_key = 'visited_' . sanitize_text_field($_GET['unique']);

            if (get_transient($unique_key)) {
                wp_safe_redirect(home_url(), 302);
                exit;
            } else {
                set_transient($unique_key, true, 5 * MINUTE_IN_SECONDS);
            }
        }
    }
}

add_action('init', 'add_specific_rewrite_rule_for_thank_you_page');

function add_specific_rewrite_rule_for_thank_you_page() {
    $thank_you_page_id = YOUR PAGE ID;

    if (is_admin()) return;

    $post = get_post($thank_you_page_id);

    if ($post) {
        add_rewrite_rule(
            '^' . $post->post_name . '/([a-zA-Z0-9]+)/?$',
            'index.php?page_id=' . $thank_you_page_id,
            'top'
        );

        if (!get_option('thank_you_page_rewrite_flushed')) {
            flush_rewrite_rules();
            update_option('thank_you_page_rewrite_flushed', true);
        }
    }
}