If you use jsonlint to validate the response of the url directly from browser you will find that the output is not a valid json response. hence you are unable to decode it. All you need to do is remove html tags which are hidden and hotel_id content and and issues with new lines . After solving those issues it becomes a valid json response. and there you go.
<?php
$base_url = "https://www.the-worldwide.com/wp-content/themes/thewebconz/Live-6-cid/functions.php";
$data = [
"action" => "Hotel_Description",
"hotel_id" => 438271,
"cid" => 457428,
];
$config = [
"apiKey" => "5jjdvgnq9aug1a4ucvatvq4b8u",
"ModeType" => "Live",
"secret" => "9hs897nn3e9av"
];
function buildUrl($base_url, $data, $config)
{
$url = $base_url."?";
$data_uri = "";
foreach ($data as $data_key => $data_value) {
$data_uri .= "$data_key=$data_value&";
}
$config_uri = "";
foreach ($config as $config_key => $config_value) {
$config_uri .= "$config_key=$config_value&";
}
$url= $base_url."?".$data_uri.rtrim($config_uri, "&");
unset($data_uri);
unset($config_uri);
return $url;
}
$url = buildUrl($base_url, $data, $config);
$content = file_get_contents($url);
$new_content = str_replace("<HotelInformationRequest><hotelId>".$data['hotel_id']."</hotelId><options>0</options></HotelInformationRequest>", "", $content);
$json_content = str_replace("\n", " ", $new_content);