Exemplo upload

$app = new \Slim\App();

$app->post('/', function ($request, $response, $args) {

    $files = $request->getUploadedFiles();

    if (empty($files['image'])) {
        return $response->withStatus(200)->write('No files.');
    }

    $file = $files['image'];

    if ($file->getError() === UPLOAD_ERR_OK) {

        $extension = pathinfo($file->getClientFilename(), PATHINFO_EXTENSION);
        $basename = bin2hex(random_bytes(8)); // see http://php.net/manual/en/function.random-bytes.php
        $filename = sprintf('%s.%0.8s', $basename, $extension);
        $file->moveTo(__DIR__ . '/uploads' . DIRECTORY_SEPARATOR . $filename);

        return $response->withStatus(200)->write('File uploaded.');
    }

    return $response->withStatus(200)->write('Error to upload.');

});

$app->run();