Creating Symfony Forms with Validation programmatically

symfony_forms.php

<?php

$builder = Validation::createValidatorBuilder();
$builder->addYamlMapping('/path/to/validation.yml');

$validator = $builder->getValidator();

$extensions = array(
    new ValidatorExtension($validator)
);

$formFactory = Forms::createFormFactoryBuilder()
    ->addExtensions($extensions)
    ->getFormFactory();