public function setLevel($min = null, $max = null)
    {
        // Null for default allows easier calling to set
        // a maximum level only
        if (!$min || !Logger::isLogLevel($min)) {
            $min = LogLevel::DEBUG;
        }

        if (!$max || !Logger::isLogLevel($max)) {
            $max = LogLevel::EMERGENCY;
        }

        $this->minimumLevel = Logger::$levels[$min];
        $this->maximumLevel = Logger::$levels[$max];
    }