Problems with SoapClient and local_cert

Hello,

I'm trying to connect to a service that requires HTTPS authentication, I
follow the steps of PHP manual doing this:

$client = new SoapClient("https://IP/wsapis?swdl", array(
'trace' => true,
'local_cert' => 'C:\\myCert.pem',
'passphrase' => 'myPassphrase'
));

But I can't access to remote file, when I try to connect I get this error:

*PHP* Fatal *error*: Uncaught SoapFault exception: [*WSDL*]
SOAP-*ERROR*: *Parsing
WSDL*: Couldn't load from 'https://IP/*wsapis?wsdl*'

Is necesary to have installed special libraries?

Any ideas?

Thanks.