将SOAP转换为PHP调用函数

I'm trying to learn how to use SoapUI to integrate Web Services to my website. I've been trying to follow PHP's documentation, but it is very confusing. My question is: how can I translate this soap code to PHP, so I can call the SOAP function. This is what I got so far:

  $wsdl = "http://api.rlcarriers.com/1.0.2/ShipmentTracingService.asmx?wsdl";

  $request = [
'APIKey' => 'xxxxxxxxxxxxxxxxxxxxxx',
'traceNumbers' => $pro,
'TraceType' => 'PRO',
'FormatResults' => 'false',
'IncludeBlind' => 'false',
'OutputFormat' => 'Standard'
];

  $client = new SoapClient($wsdl);

  $result = $client->TraceShipment($request);  

  print_r($result); 

However, this is not working. I don't know what I'm doing wrong. I appreciate any help provided. I've spent hours trying to figure it out and it's driving me crazy. This is the soap request code that I get with SoapUI by following this wsdl file: http://api.rlcarriers.com/1.0.2/ShipmentTracingService.asmx?wsdl

<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:rlc="http://www.rlcarriers.com/">
       <soap:Header/>
       <soap:Body>
          <rlc:TraceShipment>
             <!--Optional:-->
             <rlc:APIKey>******************</rlc:APIKey>
             <!--Optional:-->
             <rlc:request>
                <!--Optional:-->
                <rlc:TraceNumbers>
                   <!--Zero or more repetitions:-->
                   <rlc:string>143248716</rlc:string>
                </rlc:TraceNumbers>
                <rlc:TraceType>PRO</rlc:TraceType>
                <rlc:FormatResults>false</rlc:FormatResults>
                <rlc:IncludeBlind>false</rlc:IncludeBlind>
                <rlc:OutputFormat>Standard</rlc:OutputFormat>
                <!--Optional:-->
                <rlc:CustomerData></rlc:CustomerData>
             </rlc:request>
          </rlc:TraceShipment>
       </soap:Body>
    </soap:Envelope>

First mistake is to use the function name as a method of the SoapClient.

Correct is to use native method SoapClient::__soapCall() and the function name use as first parameter like this:

$client = new SoapClient($wsdl);
$result = $client->__call('TraceShipment', $request);

For easier debugging use the try...catch block that gave you access to messages returned from the server:

try {
  $result = $client->__soapCall('TraceShipment', $request);
} catch (Exception $e) {
  print_r($e);
  print_r($client);
}

Second mistake
The arguments $request should be an array of associative array, ie two level array, to be accepted by SoapServer:

$request = [[
  //...
]];

Third mistake
The mandatory arguments are

<s:element minOccurs="0" maxOccurs="1" name="APIKey" type="s:string"/>
<s:element minOccurs="0" maxOccurs="1" name="request" type="tns:ShipmentTracingRequest"/>

So do update your $request array by the request key (updated based on Carlos post):

$request = [[
      'APIKey' => 'xxxxxxxxxxxxxxxxxxxxxx',
      'request' => [
          'TraceNumbers' => [
              'string' => $pro
          ],
          'TraceType' => 'PRO',
          'FormatResults' => 'false',
          'IncludeBlind' => 'false',
          'OutputFormat' => 'Standard'
      ]
]];

When fixed you could get response like:

stdClass Object
(
    [TraceShipmentResult] => stdClass Object
        (
            [WasSuccess] => 1
            [Messages] => stdClass Object
                (
                )

            [Result] => stdClass Object
                (
                )
        )
)

I don't know if anyone will ever need this, but I figured out the problem. I'm just learning about SOAP now, and realized that in order to translate the SOAP call to PHP one needs to treat all tags as arrays. Therefore, given the structure of the request call, the PHP request should look like this:

$request = array(
    'APIKey' => '***********************',
    'request' => array(
        'TraceNumbers' => array(
            'string' => $pro
            ),
        'TraceType' => 'PRO',
        'FormatResults' => 'false',
        'IncludeBlind' => 'false',
        'OutputFormat' => 'Standard'
    )
);