Soap over SSL - 请协助测试环境中的证书问题

I am attempting to connect to a soap service that requires a client certificate. I am currently developing from localhost with XAMPP.

The file I received (client certificate) from the SOAP service provider came to me as a plain .txt file. I have no idea what format it is in, but I renamed it to.crt and it installed fine in Windows 10 - The service works in SoapUI.

Steps I took:

1) Saved the certificate as soap.service.crt

2) Installed the certificate (Windows 10) - This got SoapUI working. The request and response works fine.

Now, I need to get this working in Apache / PHP

Here is how I set up:

(Request array not shown. Target address is https.)

$my_cert_file = "c:\\xammp\htdocs\website\trunk\soap.service.crt";

$wsdl = "https://some.com/arbitrary/service?wsdl"; 

$context = stream_context_create([
    'ssl' => [
        // set some SSL/TLS specific options
        'verify_peer' => false,
        'verify_peer_name' => false,
        'allow_self_signed' => true
    ]
]);


try 
{
    $client = new SoapClient ($wsdl, array('trace' => 1, 'local_cert'=>$my_cert_file, 'context'=>$context));
}

catch(Exception $e) 
{
    echo $e->getMessage();
    return;
}   

$client->__setSoapHeaders(soapClientWSSecurityHeader());  
// I am calling a WSS method - checked and works fine in SoapUI.

$result     = $client->authenticateMember($params);
$request    = $client->__getLastRequest();
$response   = $client->__getLastResponse();

My actual question(s):

I read that I have to include a key in my certificate, essentially my private key concatenated with the received certificate.

1) What format does this concatenated certificate need to be in? 2) How do I generate this private key - does the client certificate need to be input (in other words, is the private key generated "from" the .crt file?) 3) How do I go about doing all this - what tool do I use? (I do have access to an Ubuntu 16.04 vm) 4) Does the call setup look correct to you?

Finally, here is the error I am getting:

SOAP-ERROR: Parsing WSDL: Couldn't load from 'https://some.com/arbitrary/service?wsdl' : failed to load external entity "https://https://some.com/arbitrary/service?wsdl"