Expedia PHP SimpleXML API Code Example - See as well http://stackoverflow.com/a/16568432/367456

output-beautified.xml

<?xml version="1.0"?>
<ns2:HotelListResponse xmlns:ns2="http://v3.hotel.wsapi.ean.com/">
  <?xml-stylesheet type="text/xsl" href="css/stile.xsl"?>
  <customerSessionId>...

simplexml-expedia-api.php

<?php
/*
 * Some little $_POST values and $apiKey are already set.
 */
$_POST['datepicker1'] = '2013-06-12';
$_POST['datepicker2'] = '2013-06-16';

$apiKey = '.....';

$destination = 'napoli';
$adults = '2';

/*
 * Create the XML for the request with hepl of SimpleXML
 */
$url = "https://api.eancdn.com/ean-services/rs/hotel/v3/list";

$xml = new SimpleXMLElement('<HotelListRequest/>');
$xml->destinationString = $destination;
$xml->arrivalDate       = $_POST['datepicker1'];
$xml->departureDate     = $_POST['datepicker2'];
$xml->RoomGroup->Room->numberOfAdults = $adults;

/*
 * Set the parameters for the API request
 */
$params = [
    'cid'          => 55505,
    'minorRev'     => 99,
    'apiKey'       => $apiKey,
    'locale'       => 'it_IT',
    'currencyCode' => 'EUR',
    'xml'          => $xml->asXML(),
];

/*
 * Set the stream context for the API request
 */
$context = stream_context_create(['http' => [
    'method' => 'POST',
    'header' => [
        'Accept: application/xml',
        'Content-Type: application/x-www-form-urlencoded',
    ],
    'content' => http_build_query($params),
]]);
libxml_set_streams_context($context);


/*
 * Perform the API request (and here: insert the stylesheet PI)
 */
$hotel = simplexml_load_file($url, 'MySimpleXMLElement');
$hotel->addProcessingInstruction('xml-stylesheet', 'type="text/xsl" href="css/stile.xsl"');
$hotel->asXML('php://output');