nouveau-theatre-de-besancon/site/controllers/search.php

<?php

return function ($site) {

  $query   = get('q');
  $allEvents = page('programme')->children()->children();
  $results = $allEvents->search($query, 'title|authors|categories');

  return [
    'query'   => $query,
    'results' => $results,
  ];

};