Removing the Accept header when retrieving waxlrs XML configuration returns no error

file_get_contents_waxlrs_xml_no_accept_header.php

<?php 

$configuration_url = 'https://uomedtest.waxlrs.com/lti?u=https://uomedtest.waxlrs.com/embed/mostpopular';


//$opts = array(
//    'http' => array(
//        'header' => "Accept: application/xml\r\n"
//    )
//);
//
//$context = stream_context_create($opts);
//$config_string = file_get_contents($configuration_url, false, $context);

$config_string = file_get_contents($configuration_url, false);

$config = simplexml_load_string($config_string);
$launch_url = (string) $config->children('blti', true)->launch_url;

echo $launch_url; /* returns https://uomedtest.waxlrs.com/embed/mostpopular */

?>