Missing Class definition?

<?php

$request = new HttpRequest();
$request->setUrl('https://api.ltl.xpo.com/rating/1.0/ratequotes');
$request->setMethod(HTTP_METH_POST);

$request->setQueryData(array(
  'format' => 'XML'
));

$request->setHeaders(array(
  'cache-control' => 'no-cache',
  'content-type' => 'application/xml',
  'authorization' => 'Bearer 5ce5e6e3304fd4e069b1c00f1c1f9bab'
));

$request->setBody('<?xml version="1.0" encoding="UTF-8"?>
<GetXpoLtlRateQuoteRqst xmlns="http://www.ltl.xpo.com/API/LTLRatingAPI">
<shipmentInfo>
    <paymentTermCd>P</paymentTermCd>
    <accessorials>
        <accessorialCd>DNC</accessorialCd>
        <accessorialCd>GUR</accessorialCd>
    </accessorials>
    <commodity>
        <grossWeight>
            <weight>500</weight>
            <weightUom>lbs</weightUom>
        </grossWeight>
        <nmfcClass>100</nmfcClass>
        <hazmatInd>false</hazmatInd>
    </commodity>
    <shipmentDate>2018-11-19</shipmentDate>
    <shipper>
        <address>
	<acctInstId>117258878</acctInstId>
            <postalCd>93727</postalCd>
        </address>
    </shipper>
    <consignee>
        <address>
            <postalCd>92027</postalCd>
        </address>
    </consignee>
</shipmentInfo>
</GetXpoLtlRateQuoteRqst>
');

try {
  $response = $request->send();

  echo $response->getBody();
} catch (HttpException $ex) {
  echo $ex;
}