codigo para crear una credencial con imagen

<?php

class Heroku_credential{
  $username = $_POST['username'];
  $password = $_POST['password'];
  $imagen = $_POST['image'];

  $credential = $username . ":" . $password;
  $base64 = base64_encode($credential);
  $header = "Authorization: Basic " . $base64;

  $curl = curl_init();
  curl_setopt($curl, CURLOPT_URL, "https://api.heroku.com/apps");
  curl_setopt($curl, CURLOPT_HTTPHEADER, array($header));
  curl_setopt($curl, CURLOPT_POSTFIELDS, array("name" => $imagen));
  curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
  curl_setopt($curl, CURLOPT_HEADER, 1);

  $data = curl_exec($curl);
  curl_close($curl