curl \
  -X POST \
  -H "Content-Type: application/x-www-form-urlencoded" \
  -d "grant_type=client_credentials" \
  -d "client_id=CLIENT_ID" \
  -d "client_secret=CLIENT_SECRET" \
  "https://accountsandbox.hubintent.com/oauth/token"

<?php

$curl = curl_init();

curl_setopt_array($curl, array(
  CURLOPT_URL => "https://accountsandbox.hubintent.com/oauth/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=client_credentials&client_id=CLIENT_ID&client_secret=CLIENT_SECRET",
  CURLOPT_HTTPHEADER => array(
    "cache-control: no-cache",
    "content-type: application/x-www-form-urlencoded"
  ),
));

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

var qs = require("querystring");
var http = require("https");

var options = {
  "method": "POST",
  "hostname": "accountsandbox.hubintent.com",
  "port": null,
  "path": "/oauth/token",
  "headers": {
    "content-type": "application/x-www-form-urlencoded",
    "cache-control": "no-cache"
  }
};

var req = http.request(options, function (res) {
  var chunks = [];

  res.on("data", function (chunk) {
    chunks.push(chunk);
  });

  res.on("end", function () {
    var body = Buffer.concat(chunks);
    console.log(body.toString());
  });
});

req.write(qs.stringify({ grant_type: 'client_credentials',
  client_id: 'CLIENT_ID',
  client_secret: 'CLIENT_SECRET' }));
req.end();

import http.client

conn = http.client.HTTPSConnection("accountsandbox.hubintent.com")

payload = "grant_type=client_credentials&client_id=CLIENT_ID&client_secret=CLIENT_SECRET"

headers = {
    'content-type': "application/x-www-form-urlencoded",
    'cache-control': "no-cache"
    }

conn.request("POST", "/oauth/token", payload, headers)

res = conn.getresponse()
data = res.read()

print(data.decode("utf-8"))

OkHttpClient client = new OkHttpClient();

MediaType mediaType = MediaType.parse("application/x-www-form-urlencoded");
RequestBody body = RequestBody.create(mediaType, "grant_type=client_credentials&client_id=CLIENT_ID&client_secret=CLIENT_SECRET");
Request request = new Request.Builder()
  .url("https://accountsandbox.hubintent.com/oauth/token")
  .post(body)
  .addHeader("content-type", "application/x-www-form-urlencoded")
  .addHeader("cache-control", "no-cache")
  .build();

Response response = client.newCall(request).execute();

var client = new RestClient("https://accountsandbox.hubintent.com/oauth/token");
var request = new RestRequest(Method.POST);
request.AddHeader("cache-control", "no-cache");
request.AddHeader("content-type", "application/x-www-form-urlencoded");
request.AddParameter("application/x-www-form-urlencoded", "grant_type=client_credentials&client_id=CLIENT_ID&client_secret=CLIENT_SECRET", ParameterType.RequestBody);
IRestResponse response = client.Execute(request);

{
  "token_type":"bearer",
  "access_token":"bc378d50dca644816b777afd26d21e7260bb8296",
  "expires_in":3600
}