php - PayPal IPN が検証されていない

Question

次のCakePHP 2.xコードがあります

<?php
App::uses('HttpSocket', 'Network/Http');

class PaypalUtility
{
    public static function isValidPayPalIPN( $data )
    {
        $result = false;
        $HttpSocket = new HttpSocket();
        $data[ "cmd" ] = "_notify-validate";
        $response = $HttpSocket->post( 'https://www.sandbox.paypal.com/cgi-bin/webscr', $data );

        if( trim( $response->body ) == "VERIFIED" )
        {
            $result = true;
        }

        return $result;
    }
}
?>

そして、コントローラーの次のコード

debug( PaypalUtility::isValidPayPalIPN( $this->getTestIPN() ) );
debug( PaypalUtility::isValidPayPalIPN( $this->getRealIPN() ) );

public function getRealIPN()
{
    return json_decode
    (
        '{
            "mc_gross": "77.00",
            "protection_eligibility": "Eligible",
            "address_status": "confirmed",
            "payer_id": "",
            "tax": "0.00",
            "address_street": "",
            "payment_date": "16:58:02 Oct 28, 2013 PDT",
            "payment_status": "Completed",
            "charset": "windows-1252",
            "address_zip": "",
            "first_name": "",
            "mc_fee": "2.53",
            "address_country_code": "US",
            "address_name": "",
            "notify_version": "3.7",
            "custom": "5269cf50-b898-4c45-bff0-0eea48a70080",
            "payer_status": "unverified",
            "business": "",
            "address_country": "United States",
            "address_city": "",
            "quantity": "1",
            "verify_sign": "AnPnM9mwa.0sVUNKppvjyOwMkqbKAABVDC8dkcXYOK4e-cpFzVuF4YvS",
            "payer_email": "",
            "txn_id": "",
            "payment_type": "instant",
            "last_name": "",
            "address_state": "",
            "receiver_email": "",
            "payment_fee": "",
            "receiver_id": "",
            "txn_type": "web_accept",
            "item_name": "",
            "mc_currency": "USD",
            "item_number": "",
            "residence_country": "",
            "handling_amount": "0.00",
            "transaction_subject": "5269cf50-b898-4c45-bff0-0eea48a70080",
            "payment_gross": "77.00",
            "shipping": "0.00",
            "ipn_track_id": ""
        }',
        true
    );
}

public function getTestIPN()
{
    return json_decode
    (
        '{
            "residence_country": "US",
            "invoice": "abc1234",
            "address_city": "San Jose",
            "first_name": "John",
            "payer_id": "TESTBUYERID01",
            "shipping": "3.04",
            "mc_fee": "0.44",
            "txn_id": "611422392",
            "receiver_email": "seller@paypalsandbox.com",
            "quantity": "1",
            "custom": "xyz123",
            "payment_date": "22:29:21 28 Oct 2013 PDT",
            "address_country_code": "US",
            "address_zip": "95131",
            "tax": "2.02",
            "item_name": "something",
            "address_name": "John Smith",
            "last_name": "Smith",
            "receiver_id": "seller@paypalsandbox.com",
            "item_number": "AK-1234",
            "verify_sign": "AiPC9BjkCyDFQXbSkoZcgqH3hpacAaChsjNZq2jHG82F97aoFSMa6SED",
            "address_country": "United States",
            "payment_status": "Completed",
            "address_status": "confirmed",
            "business": "seller@paypalsandbox.com",
            "payer_email": "buyer@paypalsandbox.com",
            "notify_version": "2.1",
            "txn_type": "web_accept",
            "test_ipn": "1",
            "payer_status": "verified",
            "mc_currency": "USD",
            "mc_gross": "12.34",
            "address_state": "CA",
            "mc_gross1": "12.34",
            "payment_type": "echeck",
            "address_street": "123, any street"
        }',
        true
    );
}

購入者のプライバシーを保護するために、フィールドは realIPN 機能から削除されました。

コードの出力は次のとおりです: http://i.imgur.com/9xcM7hL.png

IPN シミュレーターからのデータであるテスト IPN は有効ですが、リクエストとして取得した実際のデータは無効であることがわかります。(また、paypal が realipn の検証に対して「INVALID」を返していることも確認しました。

isValidPayPalIPN 関数の何が問題なのか、または実際の IPN データが検証されないのはなぜですか? 通知バージョンと関係があると想像する必要があります。