Symfony\Installer\DownloadCommand::download PHP Method

    protected function download()
    {
        $this->output->writeln(sprintf("\n Downloading %s...\n", $this->getDownloadedApplicationType()));
        // decide which is the best compressed version to download
        $distill = new Distill();
        $symfonyArchiveFile = $distill->getChooser()->setStrategy(new MinimumSize())->addFilesWithDifferentExtensions($this->getRemoteFileUrl(), ['tgz', 'zip'])->getPreferredFile();
        /** @var ProgressBar|null $progressBar */
        $progressBar = null;
        $downloadCallback = function (ProgressEvent $event) use(&$progressBar) {
            $downloadSize = $event->downloadSize;
            $downloaded = $event->downloaded;
            // progress bar is only displayed for files larger than 1MB
            if ($downloadSize < 1 * 1024 * 1024) {
                return;
            }
            if (null === $progressBar) {
                ProgressBar::setPlaceholderFormatterDefinition('max', function (ProgressBar $bar) {
                    return Helper::formatMemory($bar->getMaxSteps());
                });
                ProgressBar::setPlaceholderFormatterDefinition('current', function (ProgressBar $bar) {
                    return str_pad(Helper::formatMemory($bar->getProgress()), 11, ' ', STR_PAD_LEFT);
                });
                $progressBar = new ProgressBar($this->output, $downloadSize);
                $progressBar->setFormat('%current%/%max% %bar%  %percent:3s%%');
                $progressBar->setRedrawFrequency(max(1, floor($downloadSize / 1000)));
                $progressBar->setBarWidth(60);
                if (!defined('PHP_WINDOWS_VERSION_BUILD')) {
                    $progressBar->setEmptyBarCharacter('░');
                    // light shade character \u2591
                    $progressBar->setProgressCharacter('');
                    $progressBar->setBarCharacter('▓');
                    // dark shade character \u2593
                }
                $progressBar->start();
            }
            $progressBar->setProgress($downloaded);
        };
        $client = $this->getGuzzleClient();
        // store the file in a temporary hidden directory with a random name
        $this->downloadedFilePath = rtrim(getcwd(), DIRECTORY_SEPARATOR) . DIRECTORY_SEPARATOR . '.' . uniqid(time()) . DIRECTORY_SEPARATOR . 'symfony.' . pathinfo($symfonyArchiveFile, PATHINFO_EXTENSION);
        try {
            $request = $client->createRequest('GET', $symfonyArchiveFile);
            $request->getEmitter()->on('progress', $downloadCallback);
            $response = $client->send($request);
        } catch (ClientException $e) {
            if ('new' === $this->getName() && ($e->getCode() === 403 || $e->getCode() === 404)) {
                throw new \RuntimeException(sprintf("The selected version (%s) cannot be installed because it does not exist.\n" . "Execute the following command to install the latest stable Symfony release:\n" . '%s new %s', $this->version, $_SERVER['PHP_SELF'], str_replace(getcwd() . DIRECTORY_SEPARATOR, '', $this->projectDir)));
            } else {
                throw new \RuntimeException(sprintf("There was an error downloading %s from symfony.com server:\n%s", $this->getDownloadedApplicationType(), $e->getMessage()), null, $e);
            }
        }
        $this->fs->dumpFile($this->downloadedFilePath, $response->getBody());
        if (null !== $progressBar) {
            $progressBar->finish();
            $this->output->writeln("\n");
        }
        return $this;
    }