PHP cURL oddness

curl.php

<?php

// This fails, but only on staging (DigitalOcean) server.
// Works fine on production (Linode) server.
// Please ignore bad security practices.
$curl = curl_init();
curl_setopt($curl, CURLOPT_URL, 'https://server.com:2143');
curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, 0);
curl_setopt($curl, CURLOPT_CUSTOMREQUEST, 'POST');
curl_setopt($curl, CURLOPT_POSTFIELDS, '<CommandQuery/>');
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($curl);

var_dump($response); // false
print_r(curl_getinfo($curl)); // Don't event get a valid HTTP response code or content type.

// This works just fine on the same staging (DigitalOcean) server.
// curl -v -k https://server.com:2143 -d '<CommandQuery/>'