Twig_Error_Syntax for “Unknown filter” with a Twig filter in Timber

Question

This has got to be simple, but I can\'t see what\'s wrong. I\'m using the simple filter example at https://twig.symfony.com/doc/1.x/advanced.html#filters with Twig 1.34 in T

Answer 1

According to documentation here (title: Adding to Twig)

it should be done like this (in functions.php):

add_filter('timber/twig', function($twig) {
   $twig->addExtension(new Twig_Extension_StringLoader());

   // add Your filters here
   $twig->addFilter(
     new Twig_SimpleFilter(
       'rot13', 
       function($string) {
         return str_rot13($string);
       }
     )
   );
   // or simply: 
   // $twig->addFilter(new Twig_SimpleFilter('rot13', 'str_rot13'));

   $twig->addFilter(
     new Twig_SimpleFilter(
       'hello', 
       function($name) {
         return 'Hello, '.$name;
       }
     )
   );

   return $twig;
});