付款后获取发票paypal for merchant api php

我的问题是，我想在支付服务器上的存储费用（pdf格式）后得到账单。我一直在看API并创建发票，但不知道如何自动获取账单

<?php

require __DIR__ . '/../bootstrap.php';
use PayPal\Api\Address;
use PayPal\Api\BillingInfo;
use PayPal\Api\Cost;
use PayPal\Api\Currency;
use PayPal\Api\Invoice;
use PayPal\Api\InvoiceAddress;
use PayPal\Api\InvoiceItem;
use PayPal\Api\MerchantInfo;
use PayPal\Api\PaymentTerm;
use PayPal\Api\Phone;
use PayPal\Api\ShippingInfo;

$invoice = new Invoice();
Invoice Info


$invoice
    ->setMerchantInfo(new MerchantInfo())
    ->setBillingInfo(array(new BillingInfo()))
    ->setNote("Medical Invoice 16 Jul, 2013 PST")
    ->setPaymentTerm(new PaymentTerm())
    ->setShippingInfo(new ShippingInfo());
Merchant Info

A resource representing merchant information that can be used to identify merchant
$invoice->getMerchantInfo()
    ->setEmail("jaypatel512-facilitator@hotmail.com")
    ->setFirstName("Dennis")
    ->setLastName("Doctor")
    ->setbusinessName("Medical Professionals, LLC")
    ->setPhone(new Phone())
    ->setAddress(new Address());

$invoice->getMerchantInfo()->getPhone()
    ->setCountryCode("001")
    ->setNationalNumber("5032141716");
Address Information

The address used for creating the invoice
$invoice->getMerchantInfo()->getAddress()
    ->setLine1("1234 Main St.")
    ->setCity("Portland")
    ->setState("OR")
    ->setPostalCode("97217")
    ->setCountryCode("US");
Billing Information

Set the email address for each billing
$billing = $invoice->getBillingInfo();
$billing[0]
    ->setEmail("example@example.com");

$billing[0]->setBusinessName("Jay Inc")
    ->setAdditionalInfo("This is the billing Info")
    ->setAddress(new InvoiceAddress());

$billing[0]->getAddress()
    ->setLine1("1234 Main St.")
    ->setCity("Portland")
    ->setState("OR")
    ->setPostalCode("97217")
    ->setCountryCode("US");
Items List

You could provide the list of all items for detailed breakdown of invoice
$items = array();
$items[0] = new InvoiceItem();
$items[0]
    ->setName("Sutures")
    ->setQuantity(100)
    ->setUnitPrice(new Currency());

$items[0]->getUnitPrice()
    ->setCurrency("USD")
    ->setValue(5);
Tax Item
You could provide Tax information to each item.
$tax = new \PayPal\Api\Tax();
$tax->setPercent(1)->setName("Local Tax on Sutures");
$items[0]->setTax($tax);
Second Item
$items[1] = new InvoiceItem();
Lets add some discount to this item.
$item1discount = new Cost();
$item1discount->setPercent("3");
$items[1]
    ->setName("Injection")
    ->setQuantity(5)
    ->setDiscount($item1discount)
    ->setUnitPrice(new Currency());

$items[1]->getUnitPrice()
    ->setCurrency("USD")
    ->setValue(5);
Tax Item
You could provide Tax information to each item.
$tax2 = new \PayPal\Api\Tax();
$tax2->setPercent(3)->setName("Local Tax on Injection");
$items[1]->setTax($tax2);

$invoice->setItems($items);
Final Discount
You can add final discount to the invoice as shown below. You could either use "percent" or "value" when providing the discount
$cost = new Cost();
$cost->setPercent("2");
$invoice->setDiscount($cost);

$invoice->getPaymentTerm()
    ->setTermType("NET_45");
Shipping Information
$invoice->getShippingInfo()
    ->setFirstName("Sally")
    ->setLastName("Patient")
    ->setBusinessName("Not applicable")
    ->setPhone(new Phone())
    ->setAddress(new InvoiceAddress());

$invoice->getShippingInfo()->getPhone()
    ->setCountryCode("001")
    ->setNationalNumber("5039871234");

$invoice->getShippingInfo()->getAddress()
    ->setLine1("1234 Main St.")
    ->setCity("Portland")
    ->setState("OR")
    ->setPostalCode("97217")
    ->setCountryCode("US");
Logo

You can set the logo in the invoice by providing the external URL pointing to a logo
$invoice->setLogoUrl('https://www.paypalobjects.com/webstatic/i/logo/rebrand/ppcom.svg');
For Sample Purposes Only.
$request = clone $invoice;

try {
Create Invoice

Create an invoice by calling the invoice->create() method with a valid ApiContext (See bootstrap.php for more on ApiContext)
    $invoice->create($apiContext);
} catch (Exception $ex) {
NOTE: PLEASE DO NOT USE RESULTPRINTER CLASS IN YOUR ORIGINAL CODE. FOR SAMPLE ONLY
    ResultPrinter::printError("Create Invoice", "Invoice", null, $request, $ex);
    exit(1);
}
NOTE: PLEASE DO NOT USE RESULTPRINTER CLASS IN YOUR ORIGINAL CODE. FOR SAMPLE ONLY
 ResultPrinter::printResult("Create Invoice", "Invoice", $invoice->getId(), $request, $invoice);

return $invoice;