PHP retrieve POST result - php

Question

I'm trying to create an App for 'Exact Online' but i'm having a little bit of a problem with the OAuth security authentication
https://developers.exactonline.com/#OAuth_Tutorial.html%3FTocPath%3DAuthentication%7C_____2
After making my first authentication request and logging in I recieve a code.
With this code I can obtain an Token for making api calls.
if (!empty($_GET["code"])){
$code = $_GET["code"];
getting the code works so far. But when I try to make a new request (for the token) I get no response data.
My Code is as follows:
$data = array(
'code' => $code,
'redirect_uri' => 'http://****/asdf2.php',
'grant_type' => 'authorization_code',
'client_id' => '******-****-****-******-*****',
'client_secret' => '*********'
);
// Create map with request parameters
// Build Http query using params
$query = http_build_query ($data);
// Create Http context details
$contextData = array (
'method' => 'POST',
'header' => "Connection: close\r\n".
"Content-Length: ".strlen($query)."\r\n",
'content'=> $query );
// Create context resource for our request
$context = stream_context_create (array ( 'http' => $contextData ));
// Read page rendered as result of your POST request
$result = file_get_contents (
'https://start.exactonline.nl/api/oauth2/token', // page url
false,
$context);
// Server response is now stored in $result variable so you can process it
if (!empty($result)){
echo "success";
}else{
echo "no result";
}
}else {
echo "error";
}
$result is always empty, what could be the problem. I've checked my client_id and secret multiple times.
After changing it to cUrl it still didn't work:
$result = get_oauth2_token($code);
// Server response is now stored in $result variable so you can process it
if (!empty($result)){
echo "success";
}else{
echo "no result";
}
}else {
echo "error";
}
/*
Function
*/
function get_oauth2_token($code) {
global $client_id;
global $client_secret;
global $redirect_uri;
$oauth2token_url = "https://start.exactonline.nl/api/oauth2/token";
$clienttoken_post = array(
'code' => $code,
'redirect_uri' => 'http://*****/asdf2.php',
'grant_type' => 'authorization_code',
'client_id' => '{*******}',
'client_secret' => '******'
);
$curl = curl_init($oauth2token_url);
curl_setopt($curl, CURLOPT_POST, true);
curl_setopt($curl, CURLOPT_POSTFIELDS, $clienttoken_post);
curl_setopt($curl, CURLOPT_HTTPAUTH, CURLAUTH_ANY);
curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
$json_response = curl_exec($curl);
curl_close($curl);
$authObj = json_decode($json_response);
if (isset($authObj->refresh_token)){
//refresh token only granted on first authorization for offline access
//save to db for future use (db saving not included in example)
global $refreshToken;
$refreshToken = $authObj->refresh_token;
}
$accessToken = $authObj->access_token;
return $accessToken;
}

Answer 1

The documentation shows that client_id should be inside curly braces. So I think it should be:
'client_id' => '{******-****-****-******-*****}',