Sending HTTP request using Guzzle - php

Question

I am trying to send a post request using Guzzle 6 http client. I am sending two requests one with content type as application/x-www-form-urlencoded (form_params in Guzzle) and the other as application/json (json in Guzzle).
I initialise the client as below (forms_params and json respectively):
$data1 = array("c1" => "a", "c2" => null)
$client = new Client();
$response = $client->post(
"http://localhost/callback",
array(
"form_params" => $data1, // send as x-www-form-urlencoded
)
);
$data2 = array("c1" => "a", "c2" => null)
$client = new Client();
$response = $client->post(
"http://localhost/callback",
array(
"json" => $data2, // send as json
)
);
The response that I receive does have not identical data/body:
Output for form_params : Data -> {"c1":"a"}
Output for json : Data -> {"c1":"a","c2":null}
I am not understanding why it does not send identical data for above requests. Could this be a bug in Guzzle? Is there any way to solve this (apart from removing nulls before sending request)?
UPDATE : As requested endpoint code (both requests are read using same code)
if ($$_SERVER["CONTENT_TYPE"] == "application/json") {
$jsonstr = file_get_contents("php://input");
$formData = json_decode($jsonstr, true);
} else {
$formData = $_POST;
}
echo "Data -> " . json_encode($formData);
UPDATE 2 : I went through the links provided in comments about this being expected behaviour in Guzzle.
But why I asked this question in first place is because I faced an issue of signature mismatch.
When I send the request, I add a header with a signature which is nothing but hash_hmac("sha256", json_encode($data), "secret_key"). So I get different signatures when sending data as json and form_params (since the data received is different in case of form_params as null values are discarded/not sent). First, I thought it might be because of a bug in Guzzle but it isn't.
Is there anyway to solve this signature issue?

Answer 1

As Jon Stirling and Lawrence Cherone noticed already, it's not a bug according to Guzzle's authors.
So the solution for you is to cast values to a string for form_params. It makes sense, because URL encoded format (unlike JSON) doesn't have types (all is a string). And you everyone defines own conversion rules. In PHP (using http_build_query) it works like this, skipping nulls at all.