actions_backend.php

<?php

if(@$_GET["debug"] !== null) {
	error_reporting(E_ALL);
	ini_set("display_errors", 1);
}

$url="https://api.github.com/gists/";

$dlgitlab_url=$url."425549fbcb38834e551aea7521f5b9b1";
$dlvm_url=$url."cf4f8f439e8058c2b5b60d83ce1ad3a9";

$action=@$_GET["action"];
switch($action) {
  case "download-vm":
    get_latest_release($dlvm_url);
    break;

  case "download-gitlab":
    get_latest_release($dlgitlab_url);
    break;

  default:
    die("Not recognized action '".$action."'!");
    break;
}

function get_latest_release($url)
{
    $contents = json_decode(curl($url), true);
    $gist_content = json_decode(curl($contents["history"][0]["url"]), true);

    $files = $gist_content["files"];
    $keys = array_keys($files);
    return $files[$keys[0]]["raw_url"];
}

function curl($url)
{
    $context = stream_context_create(
        array(
            "http" => array(
                "header" => "User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/50.0.2661.102 Safari/537.36"
            )
        )
    );

	return file_get_contents($url, false, $context);
}