app\components\Command::log PHP Method

    public static function log($message)
    {
        if (empty(\Yii::$app->params['log.dir'])) {
            return;
        }
        $logDir = \Yii::$app->params['log.dir'];
        if (!file_exists($logDir)) {
            return;
        }
        $logFile = realpath($logDir) . '/walle-' . date('Ymd') . '.log';
        if (self::$logFile === null) {
            self::$logFile = fopen($logFile, 'a');
        }
        $message = date('Y-m-d H:i:s -- ') . $message;
        fwrite(self::$logFile, $message . PHP_EOL);
    }