Guzzle not sending PSR-7 POST body correctly - guzzle

Question

It is either not being sent, or not being received correctly. Using curl direct from the command line (using the -d option) or from PHP (using CURLOPT_POSTFIELDS) does work.
I start with a PSR-7 request:
$request = GuzzleHttp\Psr7\Request('POST', $url);
I add authentication header, which authenticates against the API correctly:
$request = $request->withHeader('Authorization', 'Bearer ' . $accessToken);
Then I add the request body:
// The parameter for the API function
$body = \GuzzleHttp\Psr7\stream_for('args=dot');
$request = $request->withBody($body);
I can send the message to the API:
$client = new \GuzzleHttp\Client();
$response = $client->send($request, ['timeout' => 2]);
The response I get back indicates that the "args" parameter was simply not seen by the API. I have tried moving the authentication token to the args:
'args=dot&access_token=123456789'
This should work, and does work with curl from the command line (-d access_token=123456789) but the API fails to see that parameter also when sending cia curl (6.x) as above.
I can see the message does contain the body:
var_dump((string)$request->getBody());
// string(8) "args=dot"
// The "=" is NOT URL-encoded in any way.
So what could be going wrong here? Are the parameters not being sent, or are they being sent in the wrong format (maybe '=' is being encoded?), or is perhaps the wrong content-type being used? It is difficult to see what is being sent "on the wire" when using Guzzle, since the HTTP message is formatted and sent many layer deep.
Edit: Calling up a local test script instead of the remote API, I get this raw message detail:
POST
CONNECTION: close
CONTENT-LENGTH: 62
HOST: acadweb.co.uk
USER-AGENT: GuzzleHttp/6.1.1 curl/7.19.7 PHP/5.5.9
args=dot&access_token=5e09d638965288937dfa0ca36366c9f8a44d4f3e
So it looks like the body is being sent, so I guess something else is missing to tell the remote API how to interpret that body.
Edit: the command-line curl that does work, sent to the same test script, gives me two additional header fields in the request:
CONTENT-TYPE: application/x-www-form-urlencoded
ACCEPT: */*
I'm going to guess it is the content-type header which is missing from the Guzzle request which is the source of the problem. So is this a Guzzle bug? Should it not always sent a Content-Type, based on the assumptions it makes that are listed in the documentation?

Answer 1

The Content-Type header was the issue. Normally, Guzzle will hold your hand and insert headers it deems necessary, and makes a good guess at the Content-Type based on what you have given it, and how you have given it.
With Guzzle's PSR-7 messages, none of that hand-holding is done. It strictly leaves all the headers for you to handle. So when adding POST parameters to a PSR-7 Request, you must explicitly set the Content-Type:
$params = ['Foo' => 'Bar'];
$body = \GuzzleHttp\Psr7\stream_for(http_build_query($params));
$request = $request->withBody($body);
$request = $request->withHeader('Content-Type', 'application/x-www-form-urlencoded');
The ability to pass in the params as an array and to leave Guzzle to work out the rest, does not apply to Guzzle's PSR-7 implementation. It's a bit clumsy, as you need to serialise the POST parameters into a HTTP query string, and then stick that into a stream, but there you have it. There may be an easier way to handle this (e.g. a wrapper class I'm not aware of), and I'll wait and see if any come up before accepting this answer.
Be aware also that if constructing a multipart/form-data Request message, you need to add the boundary string to the Content-Type:
$request = $request->withHeader('Content-Type', 'multipart/form-data; boundary=' . $boundary);
Where $boundary can be something like uniq() and is used in construction the multipart body.

Answer 2

The GuzzleHttp\Client provides all necessary wrapping.
$response = $client->post(
$uri,
[
'auth' => [null, 'Bearer ' . $token],
'form_params' => $parameters,
]);
Documentation available Guzzle Request Options
Edit: However, if your requests are being used within GuzzleHttp\Pool then, you can simply everything into the following:
$request = new GuzzleHttp\Psr7\Request(
'POST',
$uri,
[
'Authorization' => 'Bearer ' . $token,
'Content-Type' => 'application/x-www-form-urlencoded'
],
http_build_query($form_params, null, '&')
);