CURL POST请求返回错误55时我的请求有什么问题吗

Question

我正在尝试使用php中的curl发出POST请求，并收到curl错误＃55。一直到处逛逛，看不到有关此错误的太多信息。我认为我的要求没有错。

$curl = curl_init();

$encoded = base64_encode("12345:12345");

curl_setopt($curl, CURLOPT_URL, "https://accounts.spotify.com/api/token");
curl_setopt($curl, CURLOPT_HTTPHEADER, array(
    "Content-Type: application/json\r\n",
    "Accept: application/json",
    'Authorization: Basic ' . $encoded,
    "Accept: application/json"));
curl_setopt($curl, CURLOPT_POST, true);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl, CURLOPT_POSTFIELDS, array(
   "grant_type" => "refresh_token",
    "refresh_token" => 'CxRmNSepUaA41Zs8xIN68fC2wYbRrsrQWKE9547fF6Q12LDOpr551xb95K62+EqnGq6glEHXF4R3qgtgCnOVpr9wFAaxta5/iBKzYBqk+2B442qgiUQu7GyAm+mD1ick3vGrdlZgEEpr/U9EcVVGqXf3XN1EhlZa/vYGgO2opkKedFgbN53Hdd+xQ=='
));

$server_output = curl_exec($curl);
$err = curl_errno($curl);
print("CURL error: ");
print($err);
print($server_output);