functions.php

<?php
/**
 * Timber starter-theme
 * https://github.com/timber/starter-theme
 *
 * @package  WordPress
 * @subpackage  Timber
 * @since   Timber 0.1
 */

if ( ! class_exists( 'Timber' ) ) {
	add_action( 'admin_notices', function() {
		echo '<div class="error"><p>Timber not activated. Make sure you activate the plugin in <a href="' . esc_url( admin_url( 'plugins.php#timber' ) ) . '">' . esc_url( admin_url( 'plugins.php' ) ) . '</a></p></div>';
	});

	add_filter('template_include', function( $template ) {
		return get_stylesheet_directory() . '/static/no-timber.html';
	});

	return;
}

Timber::$dirname = array( 'templates', 'views' );
/** Start Timber! */

class StarterSite extends Timber\Site {
	/** Add timber support. */
	public function __construct() {
		add_theme_support( 'post-formats' );
		add_theme_support( 'post-thumbnails' );
		add_theme_support( 'menus' );
		add_theme_support( 'html5', array( 'comment-list', 'comment-form', 'search-form', 'gallery', 'caption' ) );
		add_filter( 'timber_context', array( $this, 'add_to_context' ) );
		add_filter( 'get_twig', array( $this, 'add_to_twig' ) );
		add_action( 'init', array( $this, 'register_post_types' ) );
		add_action( 'init', array( $this, 'register_taxonomies' ) );
		parent::__construct();
	}
	/** This is where you can register custom post types. */
	public function register_post_types() {

	}
	/** This is where you can register custom taxonomies. */
	public function register_taxonomies() {

	}

	/** This is where you add some context
	 *
	 * @param string $context context['this'] Being the Twig's {{ this }}.
	 */
	public function add_to_context( $context ) {
		$context['foo'] = 'bar';
		$context['stuff'] = 'I am a value set in your functions.php file';
		$context['notes'] = 'These values are available everytime you call Timber::get_context();';
		$context['menu'] = new Timber\Menu();
		$context['site'] = $this;
		return $context;
	}

	/** This Would return 'foo bar!'.
	 *
	 * @param string $text being 'foo', then returned 'foo bar!'.
	 */
	public function myfoo( $text ) {
		$text .= ' bar!';
		return $text;
	}

	/** This is where you can add your own functions to twig.
	 *
	 * @param string $twig get extension.
	 */
	public function add_to_twig( $twig ) {
		$twig->addExtension( new Twig_Extension_StringLoader() );
		$twig->addFilter( new Twig_SimpleFilter( 'myfoo', array( $this, 'myfoo' ) ) );
		return $twig;
	}

}

new StarterSite();