public function setHttpHeaders($httpHeaders = null)
	{
		// use global _SERVER if $httpHeaders aren't defined
		if (!is_array($httpHeaders) || !count($httpHeaders)) {
			$httpHeaders = $_SERVER;
		}

		// clear existing headers
		$this->httpHeaders = array();

		// Only save HTTP headers. In PHP land, that means only _SERVER vars that
		// start with HTTP_.
		foreach ($httpHeaders as $key => $value) {
			if (substr($key, 0, 5) === 'HTTP_') {
				$this->httpHeaders[$key] = $value;
			}
		}

		// In case we're dealing with CloudFront, we need to know.
		$this->setCfHeaders($httpHeaders);
	}