how to return json encoded form errors in symfony

I've finally found the solution to this problem here, it only needed a small fix to comply to latest symfony changes and it worked like a charm:

The fix consists in replacing line 33

if (count($child->getIterator()) > 0) {

with

if (count($child->getIterator()) > 0 && ($child instanceof \Symfony\Component\Form\Form)) {

because, with the introduction in symfony of Form\Button, a type mismatch will occur in serialize function which is expecting always an instance of Form\Form.

You can register it as a service:

services:
form_serializer:
    class:        Wooshii\SiteBundle\FormErrorsSerializer

and then use it as the author suggest:

$errors = $this->get('form_serializer')->serializeFormErrors($form, true, true);

I am using this, it works quiet well:

/**
 * List all errors of a given bound form.
 *
 * @param Form $form
 *
 * @return array
 */
protected function getFormErrors(Form $form)
{
    $errors = array();

    // Global
    foreach ($form->getErrors() as $error) {
        $errors[$form->getName()][] = $error->getMessage();
    }

    // Fields
    foreach ($form as $child /** @var Form $child */) {
        if (!$child->isValid()) {
            foreach ($child->getErrors() as $error) {
                $errors[$child->getName()][] = $error->getMessage();
            }
        }
    }

    return $errors;
}