IOS订阅优惠-PHP生成ECDSA算法签名

<?php
use Ramsey\Uuid\Uuid;

class ItunesSignatureGenerator {
    private $appBundleID = 'www.u17.com';

    private $keyIdentifier = 'ZZZZZZZ';

    private $itunesPrivateKeyPath = '/path/to/the/file.p8;

    /**
     * @see https://developer.apple.com/documentation/storekit/in-app_purchase/generating_a_signature_for_subscription_offers
     *
     * @param $productIdentifier
     * @param $offerIdentifier
     *
     * @return Signature
     */
    public function generateSubscriptionOfferSignature($productIdentifier, $offerIdentifier)
    {
        $nonce = strtolower(Uuid::uuid1()->toString());
        $timestamp = time() * 1000;
        $applicationUsername = 'username';

        $message = implode(
            "\u{2063}",
            [
                $this->appBundleID,
                $this->keyIdentifier,
                $productIdentifier,
                $offerIdentifier,
                $applicationUsername,
                $nonce,
                $timestamp
            ]
        );

        $message = $this->sign($message);

        return new Signature(
            base64_encode($message),
            $nonce,
            $timestamp,
            $this->keyIdentifier
        );
    }

    private function sign($data)
    {
        $signature = '';

        openssl_sign(
            $data,
            $signature,
            openssl_get_privatekey('file://' . $this->itunesPrivateKeyPath),
            OPENSSL_ALGO_SHA256
        );

        return $signature;
    }
}