Flarum\Foundation\AbstractServer::registerLogger PHP Method

    protected function registerLogger(Application $app)
    {
        $logger = new Logger($app->environment());
        $logPath = $app->storagePath() . '/logs/flarum.log';
        $handler = new StreamHandler($logPath, Logger::DEBUG);
        $handler->setFormatter(new LineFormatter(null, null, true, true));
        $logger->pushHandler($handler);
        $app->instance('log', $logger);
        $app->alias('log', 'Psr\\Log\\LoggerInterface');
    }