/** @return validated or eventually sanitized value from $_SERVER or null if not present or sanitation failed
	 * @param string $name key in $_SERVER 
	 * @see HttpValidator and pnt.web.PntHttpValidator 
	 */ 
	function getServerValue($name) {
		return isSet($this->serverVars[$name]) ? $this->serverVars[$name] : null;
	}