Guzzle not behaving like CURL - php

Question

I want to migrate from pure CURL to Guzzle, but the API calls are not being registered correctly.
Working CURL (Class from here: https://stackoverflow.com/a/7716768/8461611)
...
$Curl = new CURL(); // setting all curl_opts there
// creating session
$session = explode(";", $Curl->post("http://www.share-online.biz/upv3_session.php", "username=".$un."&password=".$pw));
$session_key = $session[0];
$upload_server = $session[1];
// upload
$vars = ... // see below
var_dump(explode(";",$Curl->post($upload_server, $vars))); // works
Now the Guzzle stuff
...
$Curl = new GuzzleHttp\Client();
$jar = new GuzzleHttp\Cookie\FileCookieJar("cookie.txt", true);
//creating session
$session = explode(";", $Curl->request('POST', "http://www.share-online.biz/upv3_session.php",
["form_params" => ["username" => $un, "password" => $pw], 'cookies' => $jar])->getBody());
$session_key = $session[0];
$upload_server = $session[1];
$vars = ["username" => $un,
"password" => $pw,
"upload_session" => $session_key,
"chunk_no" => 1,
"chunk_number" => 1,
"filesize" => filesize($file),
"fn" => new CurlFile(realpath($file)),
"finalize" => 1,
"name" => "test",
"contents" => $file,
];
var_dump(
explode(";",$Curl->request(
'POST', "http://".$upload_server, ["multipart" => [$vars], 'cookies' => $jar])
->getBody()));
// outputs *** EXCEPTION session creation/reuse failed - 09-3-2017, 3:05 am ***
I assume I'm doing something wrong with cookies. They are being set as var_dump($jar); shows. API Docs : http://www.share-online.biz/uploadapi

Answer 1

First of all, Guzzle is not curl and cannot behave like curl. The only caveat is that it uses curl behind the scenes.
Here is the solution:
use GuzzleHttp\Client;
$client = new Client([
// Base URI is used with relative requests
'base_uri' => 'http://www.share-online.biz/',
'timeout' => 2.0,
]);
$response = $client->request('POST', 'upv3_session.php',
[
'form_params' => [
"username" => $un,
"password" => $pw
]
]
);
Use the output of your request like so:
$code = $response->getStatusCode(); // 200 || 400 | 500 etc
$reason = $response->getReasonPhrase();
$body = $response->getBody();
$response = $request->getBody(); //Explicitly cast to string.
$json_response = json_decode($response); //here the string response has be decoded to json string.
I hope it helps others that facing this situation

Answer 2

First of all, you have to call ...->getBody()->getContents() to get a string. Or cast body object to a string: (string) ...->getBody().
Then, you cannot use CurlFile class. Use fopen() to get a file handle and pass it directly to Guzzle like in the docs. Pay attentions that for file uploads you have to use multipart instead of form_params.