What causes the “Twig_Environment not found” error?

The library should be installed in the ThridParty folder.

Then in you controller.

PHP Code:

// If you don't use Composer, uncomment below
/*
require_once APPPATH . 'third_party/Twig-1.xx.x/lib/Twig/Autoloader.php';
Twig_Autoloader::register();
*/ 


Are you doing that?

Twig for Developers

Yes, I already did all that.