protected function setContextValue($wrapper, $name, $value, $overwrite = false)
    {
        if (!isset($this->contextOptions[$wrapper])) {
            $this->contextOptions[$wrapper] = array($name => $value);
        } elseif (!$overwrite && isset($this->contextOptions[$wrapper][$name])) {
            return;
        }
        $this->contextOptions[$wrapper][$name] = $value;
        stream_context_set_option($this->context, $wrapper, $name, $value);
    }