无法转换OTA API xml响应？

I'm trying to parse OTA service's XML response in PHP. I have tried below code but no luck.

$doc = new DOMDocument();

$doc->loadXML($response);

$XMLresults = $doc->getElementsByTagName("OTA_VehAvailRateRS");

I want to get different tags value from xml response. Can someone help me out from this? Thanks. For example i want to parse following xml response:

<?xml version="1.0"?> 
<OTA_VehAvailRateRS xmlns="http://www.opentravel.org/OTA/2003/05" TimeStamp="2018-02-28T01:12:27" Target="Test" Version="4.500" SequenceNmbr="1"> 
    <Success/> 
    <VehAvailRSCore> 
    <VehRentalCore PickUpDateTime="2018-03-13T08:00:00" ReturnDateTime="2018-03-30T08:00:00"> 
    <PickUpLocation LocationCode="TEST"/> 
    <ReturnLocation LocationCode="TEST"/> 
    </VehRentalCore> 
    <VehVendorAvails> 
    <VehVendorAvail> 
    <VehAvails> <VehAvail> 
    <VehAvailCore Status="Available"> 
    <Vehicle Code="TEST15" VendorCarType="TEST15" Description="TEST"/> 
    <RentalRate> 
    <RateDistance Unlimited="True" DistUnitName="Mile" VehiclePeriodUnitName="RentalPeriod"/> 
    <VehicleCharges> 
    <VehicleCharge Description="TEST" Amount="1299.35" CurrencyCode="" GuaranteedInd="True" Purpose="1"> <Calculation UnitCharge="33.32" UnitName="Hour"/> 
    <Calculation UnitCharge="1560.00" UnitName="Month"/> 
    <Calculation UnitCharge="499.75" UnitName="Week"/> 
    <Calculation UnitCharge="99.95" UnitName="Day"/> 
    <TaxAmounts> </TaxAmounts> 
    </VehicleCharge> 
    </VehicleCharges> 
    </RentalRate> 
    <Fees> </Fees> 
    <TotalCharge CurrencyCode="" RateTotalAmount="1299.35" EstimatedTotalAmount="1299.35"/> 
    <PricedEquips> </PricedEquips> </VehAvailCore> <VehAvailInfo> <PricedCoverages> </PricedCoverages> </VehAvailInfo> </VehAvail> </VehAvails> </VehVendorAvail> </VehVendorAvails> </VehAvailRSCore> </OTA_VehAvailRateRS>

I have found solution. I have used simplexml_load_string() function for parse response. For ex:

$xml = simplexml_load_string($finalresponse);
var_dump($xml); //getting parsed response here

For getting value of different xml nodes i have used below code:

$nodevalue = $xml->VehAvailRSCore->VehRentalCore->attributes()->PickUpDateTime; //this code gives me "2018-03-13T08:00:00" as result