Contributed by Colin O'Dell in #27580

Form events allow to dynamically modify Symfony Forms. They are used to show/hide fields depending on the value of other fields, to update the values of some field based on the value selected in another field, etc.

When using events, it's common to render the entire form and extract some parts of it using JavaScript. It's also common to do partial form submissions with AJAX. In all those cases it's useful to validate the form without actually showing the validation errors to the user.

That's why in Symfony 4.2 we've added a new clearErrors() method to remove any existing errors in the forms:

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        $task = ...;
$form = $this->createForm(TaskType::class, $task);
// ...

$form->clearErrors();

// this removes errors from the form and all its children forms
$form->clearErrors(true);
    

Because clearing the errors makes the form valid, clearErrors() should only be called after testing whether the form is valid.

Published in #Living on the edge

Justus Klein said on Nov 9, 2018 at 15:17

Nice feature, but the example seems a bit illogical. Correct me if I am mistaking but the "clearErrors"-Method only gets called if "$form->isValid()" returns true and therefore wouldn't do anything.

Benoit Galati said on Nov 9, 2018 at 15:17

Thanks for this!

There is something I don't understand in the example above. I must be missing something. How can it be useful to call $form->clearErrors(); within a condition that checked $form->isValid()? From my knowledge, form errors are always empty in this context.