Following Manual Instructions for Bootstrap 3 forms getting yml config error
In newer Symfony versions, you must use form_themes instead of form.resources:
# app/config/config.ymltwig: form_themes: ['bootstrap_3_layout.html.twig']And, you don't need to add this to your templates:
{% form_theme form 'bootstrap_3_layout.html.twig' %}You can safely remove that tag and forms will still use the Bootstrap form theme (because you configured it globally in config.yml file).
This is the official documentation about this: http://symfony.com/doc/2.6/cookbook/form/form_customization.html#making-application-wide-customizations
Probably the doc is mysaligned for the related framework version.
Try this:
config.yml
twig: form_themes: # Bootstrap: - bootstrap_3_layout.html.twigtake a look at the TWIG bundle documentation here to see a full doc of the related bundle configuration.
Hope this help