Body

Both request and response messages can contain a body.

You can check to see if a request or response has a body using the getBody() method:

$response = GuzzleHttp\get('http://httpbin.org/get');
if ($response->getBody()) {
    echo $response->getBody();
    // JSON string: { ... }
}

The body used in request and response objects is a GuzzleHttp\Stream\StreamInterface. This stream is used for both uploading data and downloading data. Guzzle will, by default, store the body of a message in a stream that uses PHP temp streams. When the size of the body exceeds 2 MB, the stream will automatically switch to storing data on disk rather than in memory (protecting your application from memory exhaustion).

You can change the body used in a request or response using the setBody() method:

use GuzzleHttp\Stream\Stream;
$request = $client->createRequest('PUT', 'http://httpbin.org/put');
$request->setBody(Stream::factory('foo'));

The easiest way to create a body for a request is using the static GuzzleHttp\Stream\Stream::factory() method. This method accepts various inputs like strings, resources returned from fopen(), and other GuzzleHttp\Stream\StreamInterface objects.

The body of a request or response can be cast to a string or you can read and write bytes off of the stream as needed.

use GuzzleHttp\Stream\Stream;
$request = $client->createRequest('PUT', 'http://httpbin.org/put', ['body' => 'testing...']);
echo $request->getBody()->read(4);
// test
echo $request->getBody()->read(4);
// ing.
echo $request->getBody()->read(1024);
// ..
var_export($request->eof());
// true

You can find out more about Guzzle stream objects in Streams.