Description:
------------
__destruct() appears to be automatically sending headers before it's ran.

Output buffering can't prevent this behaviour.

Tested on Windows XP, Apache 2.0.48

Reproduce code:
---------------
class Test {
    function __construct()
    {
        $this->_string = '__construct()<br />';
    }

    function __destruct()
    {
        if (headers_sent($file, $line)) {
            $this->_string .= 'Headers sent in ' . $file . ' on line ' . $line;
        } else {
            $this->_string .= '__destruct()';
        }
        print $this->_string;
    }
}

$test = new Test();

Expected result:
----------------
__construct()
__destruct()

Actual result:
--------------
__construct()
Headers sent in on line 0


Though headers_sent() returns true, $file and $line still have default values.