Set the body of the request
string|resource|EntityBodyInterface $body Body to use in the entity body of the request:
string $contentType Content-Type to set. Leave null to use an existing: Content-Type or to guess the Content-Type
bool $tryChunkedTransfer Try to use chunked Transfer-Encoding:
EntityEnclosingRequestInterface
RequestException if the protocol is < 1.1 and Content-Length can not be determined
public function setBody($body, $contentType = null, $tryChunkedTransfer = false);