CompositeForm::getErrors

public function getErrors($fieldName = null)
{
	$result = parent::getErrors($fieldName);
	foreach ($result as $index => $error)
	{
		if ($fieldName === null)
		{
			$result[$error->getCode()][] = $error;
			unset($result[$index]);
		}
	}
	foreach ($this->nestedForms as $name => $form)
	{
		if (is_array($form))
		{
			foreach ($form as $index => $item)
			{
				foreach ($item->getErrors() as $error)
				{
					/** @var FormError $error */
					$errorField = $name . '.' . $index . '.' . $error->getCode();
					if ($fieldName === null)
					{
						$result[$errorField][] = $error;
					}
					elseif ($errorField === $fieldName)
					{
						$result[] = $error;
					}
				}
			}
		}
		else
		{
			foreach ($form->getErrors() as $error)
			{
				/** @var FormError $error */
				$errorField = $name . '.' . $error->getCode();
				if ($fieldName === null)
				{
					$result[$errorField][] = $error;
				}
				elseif ($errorField === $fieldName)
				{
					$result[] = $error;
				}
			}
		}
	}
	return $result;
}