PHP SOAPCall Input is null - php

Question

I'm getting the following error:
Fatal error: Uncaught SoapFault exception: [s:Client] Service
operation Pickup_Cancel failed due to validation errors: Input is null
Here's my code:
$client = new SoapClient("https://etrack.postaplus.net/APIService/PostaWebClient.svc?singleWsdl", array("trace" => 1, "exception" => 0));
$params = array(
"CodeStation" => `BEY`,
"PickupNumber" => `1`,
"Reason" => `test reason`,
"Password" => `sss`,
"ShipperAccount" => `acc`,
"UserName" => `acc`,
);
$client->Pickup_Cancel($params);

Answer 1

The awnser to the question you didn't ask is probably: replace the backticks (`) by singlequotes (')
-- Edit. That was not the problem.
Here is the case. SOAP can be a pain to get going. My experience is to use a good soap class or just non-wsdl mode. Read up on this in the docs: https://www.php.net/manual/en/soapclient.soapcall.php
So don't do this:
$return = $soapClient->functionName($data);
But this:
$return = $soapClient->__SoapCall('functionName', $data);
Also get a grip on what the server wants, load the WSDL url into a client like SoapUI https://www.soapui.org/ (its free). This lets you check if the SoapServer works and how you should approach it with your call.
In your case the WSDL states this:
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:tem="http://tempuri.org/" xmlns:pos="http://schemas.datacontract.org/2004/07/PostaWebClient">
<soapenv:Header/>
<soapenv:Body>
<tem:Pickup_Cancel>
<!--Optional:-->
<tem:CLIENTINFO>
<!--Optional:-->
<pos:CodeStation>asd</pos:CodeStation>
<!--Optional:-->
<pos:Password>asd</pos:Password>
<!--Optional:-->
<pos:ShipperAccount>asd</pos:ShipperAccount>
<!--Optional:-->
<pos:UserName>asd</pos:UserName>
</tem:CLIENTINFO>
<!--Optional:-->
<tem:PickupNumber>asd</tem:PickupNumber>
<!--Optional:-->
<tem:Reason>asd</tem:Reason>
</tem:Pickup_Cancel>
</soapenv:Body>
</soapenv:Envelope>
Which translates to this PHP code:
$client = new SoapClient("https://etrack.postaplus.net/APIService/PostaWebClient.svc?singleWsdl");
$params = [
'Pickup_Cancel' => [
'CLIENTINFO' => [
'Password' => 'sss',
'ShipperAccount' => 'acc',
'UserName' => 'acc',
'CodeStation' => '',
],
'PickupNumber' => '',
'Reason' => '',
],
];
$client->__SoapCall("Pickup_Cancel", $params);
See how the array matches the WSDL xml format?
This should also give you the feedback you need to proceed. If not, its probably time to get 'real' help :) Goodluck.