private static function compareLogLevel( $a, $b )
    {
        static $defs;

        if ( !$defs ){
            $defs = array(
                'F' => LogLevel::FATAL,
                'E' => LogLevel::ERROR,
                'W' => LogLevel::WARNING,
                'I' => LogLevel::INFO,
                'D' => LogLevel::DEBUG,
                'T' => LogLevel::TRACE,
            );
        }

        $a = $defs[$a] ?? LogLevel::INFO;
        $b = $defs[$b] ?? LogLevel::INFO;

        return ($a - $b);
    }