public function signRequest(RequestInterface $request, CredentialsInterface $credentials) { if ($request instanceof EntityEnclosingRequestInterface && $request->getBody()) { $request->setHeader('X-Amz-Content-Sha256', EntityBody::getHash($request->getBody(), 'sha256')); } else { $request->setHeader('X-Amz-Content-Sha256', hash('sha256', '')); } parent::signRequest($request, $credentials); }