$client = new SoapClient('http://api.inpost.opennet.pl/api.asmx?WSDL');
$functions = $client->__getFunctions ();
var_dump ($functions);

$result = $client->__soapCall("GetTracking", array(
    'token' => array(
        'UserName' => 'demo',
        'Password' => 'demo'
    ),
    'PackageNo' => '820000013925025000000111'
), NULL);

var_dump($result);