Description:
------------
I'm trying to use HttpMessage to loosely couple interacting 
with requests in the application framework we're using here at 
Digg and ran across some really bizarre behavior. 

The problem is that when I extend HttpMessage, create a member 
variable and then attempt to write to that variable the write 
is bit-bucketed. 

Reproduce code:
---------------
<?php

class Foo
{
    protected $foo = null;
    public function test()
    {
        $this->foo = $_SERVER['SERVER_NAME'];
        var_dump($this->foo);
    }
}

class Bar extends HttpMessage
{
    protected $foo = null;
    public function test()
    {
        $this->foo = $_SERVER['SERVER_NAME'];
        var_dump($this->foo);
    }
}

$foo = new Foo();
$foo->test();

$bar = new Bar();
$bar->test();

// Results in the host from Foo and NULL from Bar

?>


Expected result:
----------------
Uh ... assigning to member variables should work? At the 
*very* least I should be able to assign to member variables I 
declare myself. 

Actual result:
--------------
Values are not assigned to member variables I've declared. 
This is forcing me to, essentially, use the decorator pattern 
as (along with HttpMessage::fromEnv() not firing my child 
class's constructor) extending this class yields unexpected 
results.