<?php
final class Payment {
    public function subscribe(array $transaction) : array {
        // 1
        $transaction = [
            'payment_method' => $transaction['payment_method'] ?? 'credit-card',
            'amount' => $transaction['total'] ?? $transaction['subtotal'] ?? 0.0,
            'currency' => $transaction['currency_code'] ?? 'USD'
        ] + $transaction;
        $model = new TransactionModel();
        $model->create($transaction);

        // 2
        $processor = $model->getProcessor($transaction);
        $transaction['processor_id'] = $processor['id'] ?? null;

        // 3
        $status = $model->process($transaction);
        $transaction['status'] = $status['success'] ?? false;

        // 4
        unset($transaction['card-number'], $transaction['ccv']);
        return $transaction;
    }
}