Description:
------------
I'm attempting to write classes that extend HttpRequest and HttpMessage.  According to the PHP.net documentation, all the properties for HttpRequest class are protected.  As such, I should allow me to send an HttpRequest, intercept the return value, create a new HttpMessage using the factory method and save that new class to the responseMessage property.

Currently there is no way to set the responseMessage property for HttpRequest.

Reproduce code:
---------------
class Client extends HttpRequest {
	
	public function send() {
		$response = parent::send();
		$this->responseMessage = Client_Message::factory($this->getRawResponseMessage());
		return $this->getResponseMessage();
	}
}

class Client_Message extends HttpMessage {
	public static function factory($raw_message = null, $class_name = null) {
		return parent::factory($raw_message, get_class());
	}
}

$c = new Client('http://www.google.com');
$c->send()
print get_class($c->getResponseMessage());

Expected result:
----------------
Client_Message

Actual result:
--------------
HttpMessage