cURL request Spotify API Unexpected status: 415 - php

Question

Here is my script for an auth request to Spotify but it returns an error. I tried changing the Content-Type, but that doesn't seem to cut it. Here is my code:
$spot_api_client = 'client';
$spot_api_secret = 'secret';
$spot_api_redirect = 'myurl';
if(isset($_GET['state']) && isset($_COOKIE['stateKey']) && $_COOKIE['stateKey'] == $_GET['state']){
$ch = curl_init();
$curlConfig = array(
CURLOPT_URL => "https://accounts.spotify.com/api/token",
CURLOPT_POST => true,
CURLOPT_RETURNTRANSFER => true,
CURLOPT_POSTFIELDS => array(
'grant_type' => 'authorization_code',
'code' => $_GET['code'],
'redirect_uri' => urlencode($spot_api_redirect),
),
CURLOPT_HTTPHEADER => array(
'Accept' => '*/*',
'User-Agent' => 'runscope/0.1',
'Authorization' => 'Basic '. base64_encode($spot_api_client.':'.$spot_api_secret),
'Content-Type'=>'application/json'
)
);
curl_setopt_array($ch, $curlConfig);
$result = curl_exec($ch);
curl_close($ch);
print_r($result);
}

Answer 1

Well, seems I found the answer based on this question :
$url = 'https://accounts.spotify.com/api/token';
$method = 'POST';
$spot_api_redirect = 'myurl';
$credentials = "client:secret";
$headers = array(
"Accept: */*",
"Content-Type: application/x-www-form-urlencoded",
"User-Agent: runscope/0.1",
"Authorization: Basic " . base64_encode($credentials));
$data = 'grant_type=authorization_code&code='.$_GET['code'].'&redirect_uri='.urlencode($spot_api_redirect);
if(isset($_GET['state']) && isset($_COOKIE['stateKey']) && $_COOKIE['stateKey'] == $_GET['state']){
unset($_COOKIE['stateKey']);
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = json_decode(curl_exec($ch), true);
curl_close($ch);
print_r($response);
}

Answer 2

Just in case of node.js / request use, point out "WTF" tag :)
request(
{
method : "POST",
url : "https://accounts.spotify.com/api/token",
json : true,
headers :
{
"Content-Type" : "application/x-www-form-urlencoded", // WTF!
"Authorization" : "Basic " + new Buffer(client_id+":"+client_secret).toString('base64')
},
body : "grant_type=client_credentials"
},
function (err, response, body)
{
if (err)
{
cb(err);
}
else
{
if (body.hasOwnProperty("access_token"))
{
access_token = body.access_token;
cb(null);
}
else
{
cb(body);
}
}
}
);