Fork of NuSOAP fixed for PHP 5.4, 5.5, 5.6, 7.0 and 7.1 (tested).
All credits belongs to official author(s): http://nusoap.sourceforge.net.
$ composer require econea/nusoap
// Config
$client = new nusoap_client('example.com/api/v1', 'wsdl');
$client->soap_defencoding = 'UTF-8';
$client->decode_utf8 = FALSE;
// Calls
$result = $client->call($action, $data);