Parse error including vendor/autoload.php

Quick update on this - I can get the library to work when I load it in an individual controller when loading it like this:

PHP Code:

include APPPATH . 'vendor/mixpanel-php/lib/Mixpanel.php';
$mp = Mixpanel::getInstance("f8d9db172d290de89a69e2b8414e497a"); 


It's selective about what events it lets me track though. I tried to track the user...

PHP Code:

$user = $this->session->userdata('email');
$mp->identify($user); 


But it wouldn't let me. I could, however, track clicks. Very strange. I was starting to write a library for it, but when I load it, same thing: 500 error. As you can see, it's pretty simple...

PHP Code:

class Mixpanel_lib
{
 public function __construct()
 {
     include APPPATH . 'vendor/mixpanel-php/lib/Mixpanel.php'; 
 
                //set token
     $mp = Mixpanel::getInstance("OUR_TOKEN");

        }
}