First, Create twig cache directory under application/cache; and give it write permission
$ mkdir -p application/cache/twig
$ chmod o+w application/cache/twig
Add the Twig config file to application/config/twig.php
Download and extract the Twig library into application/libraries. The directories should look like this
application/libraries/Twig
|-- Error
|-- Extension
|-- Filter
|-- Function
|-- Loader
|-- Node
| `-- Expression
| |-- Binary
| `-- Unary
|-- NodeVisitor
|-- Sandbox
|-- Test
`-- TokenParser
Put in your controller,
$this->load->library('twig');
$data['title'] = "Testing Twig!!";
$this->twig->display('view.html', $data);
If you want to use CodeIgniter helper functions in Twig templates do this in your controller.
$this->load->library('twig'); // load the Twig library
$this->load->helper('url'); // load the CodeIgniter URL helper
// map the base_url() function as a Twig function
$this->twig->add_function('base_url');
Then in your Twig view call the base_url() function like this
{{ base_url() }}