PHP CURL API token retrieval - php

Question

I've read everything on multiple boards and not succeeded...need the brains trust.
what i'm getting:
HTTP/1.1 400 Bad Request
preload {"error":"unsupported_grant_type"}
my goal: to retrieve the OAuth token from the FQDN/api/token endpoint
i have: endpoint, username & password (no secret or key)
i can curl from the shell and get the token - i just can't get php to do it >/
my code isn't mine anymore since i was pretty sure i was the problem but here is what i'm presently attempting to utilise: (can someone point out where i'm being a muppet!)
$curl = curl_init();
curl_setopt_array($curl, array(
CURLOPT_URL => "https://FQDN/api/token",
CURLOPT_RETURNTRANSFER => true,
CURLOPT_ENCODING => "",
CURLOPT_MAXREDIRS => 10,
CURLOPT_TIMEOUT => 30,
CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
CURLOPT_CUSTOMREQUEST => "POST",
CURLOPT_POSTFIELDS => "{\"grant_type\":\"password\",\"username\": \"user#domain.com.au\",\"password\": \"userPasswd\"}",
CURLOPT_HTTPHEADER => array(
"Content-Type: application/json",
"Content-Length: 96",
"Accept: application/json"
),
CURLOPT_HEADER => true,
CURLOPT_POST => true,
CURLOPT_HTTPAUTH => basic
));
$response = curl_exec($curl);
print_r(curl_getinfo($curl));
print_r($response);
curl_close($curl);

Answer 1

According to the comments, you need to send key value pairs:
$data = array(
"grant_type" => "password",
"username" => "username",
"password" => "password"
)
curl_setopt($ch,CURLOPT_POSTFIELDS, http_build_query($data));