自定义标头cURL PHP

Question

我有这个代码

$endpoint_url = 'https://accounts.spotify.com/api/token';

  // Creates our data array that we want to post to the endpoint
  $data_to_post = [
    'grant_type'    => 'authorization_code',
    'code'          => $code,
    'redirect_uri'  => $redirect_uri,
    'client_id'     => $client_id,
    'client_secret' => $client_secret,
  ];

  // Sets our options array so we can assign them all at once
  $options = [
    CURLOPT_URL        => $endpoint_url,
    CURLOPT_POST       => true,
    CURLOPT_POSTFIELDS => $data_to_post,
  ];

  // Initiates the cURL object
  $curl = curl_init();

  // Assigns our options
  curl_setopt_array($curl, $options);

  // Executes the cURL POST
  $results = curl_exec($curl);

  // Be kind, tidy up!
  curl_close($curl);

我需要添加标题Content-Type: application/x-www-form-urlencoded 在POST请求中。 我该怎么做？我是PHP的初学者，无法弄清楚：/