Link Stripe Checkout sales to their visits

// Express with cookie-parser (app.use(require('cookie-parser')())), where you create
// the Checkout Session; stripe = require('stripe')(process.env.STRIPE_SECRET_KEY).
app.post('/checkout', async (req, res) => {
  const visitorId = req.cookies['_tally_vid'];
  const metadata = visitorId ? { 'tally_visitor_id': visitorId } : {};
  const session = await stripe.checkout.sessions.create({
    mode: 'subscription',
    line_items: [{ price: 'price_123', quantity: 1 }],
    success_url: 'https://example.com/thanks?session_id={CHECKOUT_SESSION_ID}',
    metadata,
    // Renewals read the subscription's metadata. In payment mode, leave this line out.
    subscription_data: { metadata },
  });
  res.redirect(303, session.url);
});

// app/api/checkout/route.ts
import { cookies } from 'next/headers';
import Stripe from 'stripe';

const stripe = new Stripe(process.env.STRIPE_SECRET_KEY!);

export async function POST() {
  const visitorId = (await cookies()).get('_tally_vid')?.value;
  const metadata: Record<string, string> = visitorId ? { 'tally_visitor_id': visitorId } : {};
  const session = await stripe.checkout.sessions.create({
    mode: 'subscription',
    line_items: [{ price: 'price_123', quantity: 1 }],
    success_url: 'https://example.com/thanks?session_id={CHECKOUT_SESSION_ID}',
    metadata,
    // Renewals read the subscription's metadata. In payment mode, leave this line out.
    subscription_data: { metadata },
  });
  return Response.json({ url: session.url });
}

# Flask, where you create the Checkout Session (stripe.api_key is your secret key).
import stripe
from flask import redirect, request


@app.post("/checkout")
def checkout():
    visitor_id = request.cookies.get("_tally_vid")
    metadata = {"tally_visitor_id": visitor_id} if visitor_id else {}
    session = stripe.checkout.Session.create(
        mode="subscription",
        line_items=[{"price": "price_123", "quantity": 1}],
        success_url="https://example.com/thanks?session_id={CHECKOUT_SESSION_ID}",
        metadata=metadata,
        # Renewals read the subscription's metadata. In payment mode, leave this line out.
        subscription_data={"metadata": metadata},
    )
    return redirect(session.url, code=303)

# Rails: app/controllers/checkouts_controller.rb (Stripe.api_key is your secret key).
class CheckoutsController < ApplicationController
  def create
    visitor_id = cookies['_tally_vid']
    metadata = visitor_id ? { 'tally_visitor_id' => visitor_id } : {}
    session = Stripe::Checkout::Session.create(
      mode: 'subscription',
      line_items: [{ price: 'price_123', quantity: 1 }],
      success_url: 'https://example.com/thanks?session_id={CHECKOUT_SESSION_ID}',
      metadata: metadata,
      # Renewals read the subscription's metadata. In payment mode, leave this line out.
      subscription_data: { metadata: metadata }
    )
    redirect_to session.url, allow_other_host: true, status: :see_other
  end
end

<?php
// Where you create the Checkout Session (stripe/stripe-php).
$stripe = new \Stripe\StripeClient(getenv('STRIPE_SECRET_KEY'));

$visitorId = $_COOKIE['_tally_vid'] ?? null;
$metadata = $visitorId ? ['tally_visitor_id' => $visitorId] : [];

$session = $stripe->checkout->sessions->create([
  'mode' => 'subscription',
  'line_items' => [['price' => 'price_123', 'quantity' => 1]],
  'success_url' => 'https://example.com/thanks?session_id={CHECKOUT_SESSION_ID}',
  'metadata' => $metadata,
  // Renewals read the subscription's metadata. In payment mode, leave this line out.
  'subscription_data' => ['metadata' => $metadata],
]);

header('Location: ' . $session->url, true, 303);