title: Mandrill PHP library throws 500 error upon instantiation
body: <p>I'm moving a site from a shared host to a Digital Ocean droplet (Ubuntu 14 w/Apache). It's a Codeigniter-based PHP site. The site is all working on the DO droplet, except for our Mandrill integration. </p>
  
  <p>To narrow down whether its other code in the controller, I've put together a test page. It works at the old host but on the new site throws a 500 error:</p>
  
  <pre><code>&lt;?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
  
  class Testemail extends CI_Controller {
  
     function __construct() {
         parent::__construct();
     }
  
     function index() {
         require_once(APPPATH.'libraries/mandrill/Mandrill.php');
         // comment out the next line and the page loads fine
         $mandrill = new Mandrill('my_api_key');
  
         // there's other code here to compose and send a message
     }
  }
  // there's no closing ?&gt; in a Codeigniter file
  </code></pre>
  
  <p>Simply instantiating the Mandrill class is all it takes to throw the 500. The path to the library is correct. I've confirmed I'm using a valid key, and even created a new Mandrill key just in case. There is nothing in the Apache logs, nor in the Codeigniter logs, nor in the Mandrill API logs.</p>
  
  <p>Everything I've found so far relates to 500 errors after attempting to send a message. But, I'm not even getting that far. I've commented out all the actual sending statements to leave just what you see above and I still get the 500.</p>
  
  <p>Ubuntu 14.04, Apache 2.4.7, PHP 5.5.9, Codeigniter 2.2.6, Mandrill 1.0.55</p>
  
  <p>Edit: I can send mail using Codeigniter's email helper and the Mandrill SMTP settings. I would prefer to use the API for performance reasons. But SMTP will do for now.</p>
  
  <p>Edit: Apparently I can't easily close my own question. This is appears to be a Codeigniter issue, not a Mandrill issue. I've found some other controllers that are throwing the 500. During the transfer, I did upgrade CI which I'm sure now is the source of my troubles.</p>