Can someone explain why the XML generation in the PHP SDK is messing up?

Here's the SDK method call to createCustomerPaymentProfile():

$authNetCusObj = new AuthorizeNetCIM();
$authorizeDotNetResponse = $authNetCusObj->createCustomerPaymentProfile($custProfId, $formattedRequestData);

Here's the PHP array that's being passed into (which the XML is supposed to get generated from):

$formattedRequestData = array(
	'billTo' => array(
		'firstName' => 'TestKen',
		'lastName' => 'TestBraz',
		'address' => '123 Testa Trove',
		'city' => 'Hahahah',
		'state' => 'Utah',
		'zip' => '84440'
	),
	'payment' => array(
		'opaqueData' => array(
			'dataDescription' => 'COMMON.ACCEPT.INAPP.PAYMENT',
			'dataValue' => trim($data['dataNonce'])
		)
	)
);

Here's the (bad) XML that gets generated in the call:

<?xml version="1.0" encoding="utf-8"?>
<createCustomerPaymentProfileRequest xmlns="AnetApi/xml/v1/schema/AnetApiSchema.xsd">
	<merchantAuthentication>
		<name>Protected</name>
		<transactionKey>Protected</transactionKey>
	</merchantAuthentication>
	<customerProfileId>181</customerProfileId>
	<paymentProfile>
		<billTo>
			<0>TestKen</0>
		</billTo>
		<billTo>
			<0>TestBraz</0>
		</billTo>
		<billTo>
			<0>123 Testa Trove</0>
		</billTo>
		<billTo>
			<0>Test City</0>
		</billTo>
		<billTo>
			<0>Test State</0>
		</billTo>
		<billTo>
			<0>84440</0>
		</billTo>
		<payment>
			<dataDescription>COMMON.ACCEPT.INAPP.PAYMENT</dataDescription>
			<dataValue>eyJjfMl</dataValue>
		</payment>
	</paymentProfile>
</createCustomerPaymentProfileRequest>