SOAP-ERROR: Encoding: Violation of encoding rules

[Charles Nadeau]

Good evening,

I am installing phpVirtualBox 3.1 on a machine running Ubuntu Saucy server with VirtualBox 3.10. I used these instructions to install phpVirtualBox: https://gist.github.com/mikedevita/7461832

Upon starting phpVirtualBox, i am getting an error message saying "SOAP-ERROR: Encoding: Violation of encoding rules".
Checking the error logs of Apache2, I find these 3 lines matchng the error message:
[Sat Apr 19 22:45:17.881237 2014] [:error] [pid 1337] [client 192.168.0.5:55161] PHP Fatal error: SOAP-ERROR: Encoding: Violation of encoding rules in /var/www/vb/lib/vboxServiceWrappers.php on line 6642, referer: http://192.168.0.53/vb/
[Sat Apr 19 22:46:46.932567 2014] [:error] [pid 1519] [client 192.168.0.5:55177] PHP Fatal error: SOAP-ERROR: Encoding: Violation of encoding rules in /var/www/vb/lib/vboxServiceWrappers.php on line 6642, referer: http://192.168.0.53/vb/
[Sat Apr 19 22:47:38.257639 2014] [:error] [pid 1336] [client 192.168.0.5:55195] PHP Fatal error: SOAP-ERROR: Encoding: Violation of encoding rules in /var/www/vb/lib/vboxServiceWrappers.php on line 6642, referer: http://192.168.0.53/vb/

The line refered in the error message is:
$response = $this->connection->__soapCall('IMediumFormat_getCapabilities', array((array)$request));

From this class:
class IMediumFormat extends VBox_ManagedObject {

public function describeFileExtensions() {
$request = new stdClass();

   $request->_this = $this->handle;

   $response = $this->connection->__soapCall('IMediumFormat_describeFileExtensions', array((array)$request));

   return array((array)$response->extensions, new DeviceTypeCollection ($this->connection, (array)$response->type));

}

public function describeProperties() {
$request = new stdClass();

   $request->_this = $this->handle;

   $response = $this->connection->__soapCall('IMediumFormat_describeProperties', array((array)$request));

   return array((array)$response->names, (array)$response->description, new DataTypeCollection ($this->connection, (array)$response->types), (array)$response->flags, (array)$respons$

}

public function getId() {
$request = new stdClass();
$request->_this = $this->handle;
$response = $this->connection->__soapCall('IMediumFormat_getId', array((array)$request));
return (string)$response->returnval;
}

public function getName() {
$request = new stdClass();
$request->_this = $this->handle;
$response = $this->connection->__soapCall('IMediumFormat_getName', array((array)$request));
return (string)$response->returnval;
}

public function getCapabilities() {
$request = new stdClass();
$request->_this = $this->handle;
$response = $this->connection->__soapCall('IMediumFormat_getCapabilities', array((array)$request));
return (float)$response->returnval;
}
}

Is it a bug in the code or something I should check on my workstation. Which SOAP package should In have on my machine?

Thanks!

Charles