SOAP-ERROR: Encoding: object has no 'ACCION' property - php

Question

I have a PHP script which calls a web service created in SAP, I already validated it with soapui5 and it works fine, but PHP throws the following message:
SOAP-ERROR: Encoding: object has no 'ACCION' property
PHP code :
$url = 'https://www.ceramicaitalia.com/wssap/zwebservice1.wsdl';
$client = new SoapClient($url);
echo PHP_EOL;
$xmlr = new SimpleXMLElement("<ZWS_WEBSERVICE1></ZWS_WEBSERVICE1>");
$xmlr->addChild('login', '***');
$xmlr->addChild('password', '******');
$xmlr->addChild('ACCION', '/');
$params = new stdClass();
$params->xml = $xmlr->asXML();
$client->ZWS_WEBSERVICE1($params);
$result = $client->ZWS_WEBSERVICE1('RTA');
print_r($result);
Test in soapui5 :
Request :
<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope"
xmlns:urn="urn:sap-com:document:sap:rfc:functions">
<soap:Header/>
<soap:Body>
<urn:ZWS_WEBSERVICE1>
<ACCION>/</ACCION>
</urn:ZWS_WEBSERVICE1>
</soap:Body>
</soap:Envelope>
Response :
<env:Envelope xmlns:env="http://www.w3.org/2003/05/soap-envelope">
<env:Header/>
<env:Body>
<n0:ZWS_WEBSERVICE1Response xmlns:n0="urn:sap-com:document:sap:rfc:functions">
<RTA>1.5</RTA>
</n0:ZWS_WEBSERVICE1Response>
</env:Body>
</env:Envelope>

Answer 1

You don't need to set root element. You can to xml as array param. Library will auto set matched elements. If you have multiple element with same name but different namespace you can check SoapVar. Working sample is below.
<?php
$url = 'https://www.ceramicaitalia.com/wssap/zwebservice1.wsdl';
$client = new SoapClient($url, ['trace' => true]);
$params = ['ACCION' => '/'];
$client->ZWS_WEBSERVICE1($params);
$result = $client->ZWS_WEBSERVICE1('RTA');
print_r($result);
?>