getId() public method

The unique invoice resource identifier.
public getId ( ) : string
return string
 /**
  * @depends testSerializationDeserialization
  * @param Invoice $obj
  */
 public function testGetters($obj)
 {
     $this->assertEquals($obj->getId(), "TestSample");
     $this->assertEquals($obj->getNumber(), "TestSample");
     $this->assertEquals($obj->getUri(), "TestSample");
     $this->assertEquals($obj->getStatus(), "TestSample");
     $this->assertEquals($obj->getMerchantInfo(), MerchantInfoTest::getObject());
     $this->assertEquals($obj->getBillingInfo(), BillingInfoTest::getObject());
     $this->assertEquals($obj->getShippingInfo(), ShippingInfoTest::getObject());
     $this->assertEquals($obj->getItems(), InvoiceItemTest::getObject());
     $this->assertEquals($obj->getInvoiceDate(), "TestSample");
     $this->assertEquals($obj->getPaymentTerm(), PaymentTermTest::getObject());
     $this->assertEquals($obj->getDiscount(), CostTest::getObject());
     $this->assertEquals($obj->getShippingCost(), ShippingCostTest::getObject());
     $this->assertEquals($obj->getCustom(), CustomAmountTest::getObject());
     $this->assertEquals($obj->getTaxCalculatedAfterDiscount(), true);
     $this->assertEquals($obj->getTaxInclusive(), true);
     $this->assertEquals($obj->getTerms(), "TestSample");
     $this->assertEquals($obj->getNote(), "TestSample");
     $this->assertEquals($obj->getMerchantMemo(), "TestSample");
     $this->assertEquals($obj->getLogoUrl(), "http://www.google.com");
     $this->assertEquals($obj->getTotalAmount(), CurrencyTest::getObject());
     $this->assertEquals($obj->getPayments(), PaymentDetailTest::getObject());
     $this->assertEquals($obj->getRefunds(), RefundDetailTest::getObject());
     $this->assertEquals($obj->getMetadata(), MetadataTest::getObject());
     $this->assertEquals($obj->getAdditionalData(), "TestSample");
 }
$invoice->getShippingInfo()->setFirstName("Sally")->setLastName("Patient")->setBusinessName("Not applicable")->setPhone(new Phone())->setAddress(new Address());
$invoice->getShippingInfo()->getPhone()->setCountryCode("001")->setNationalNumber("5039871234");
$invoice->getShippingInfo()->getAddress()->setLine1("1234 Main St.")->setCity("Portland")->setState("OR")->setPostalCode("97217")->setCountryCode("US");
print var_dump($invoice->toArray());
try {
    $invoice->create($apiContext);
} catch (PayPal\Exception\PPConnectionException $ex) {
    echo "Exception: " . $ex->getMessage() . PHP_EOL;
    var_dump($ex->getData());
    exit(1);
}
?>
<html>
<head>
	<title>Direct Credit card payments</title>
</head>
<body>
	<div>
		Created Invoice:
		<?php 
echo $invoice->getId();
?>
	</div>
	<pre><?php 
var_dump($invoice->toArray());
?>
</pre>
	<a href='../index.html'>Back</a>
</body>
</html>