Contao\CoreBundle\DataContainer\PaletteManipulator::canApplyToParent PHP Метод

    private function canApplyToParent(array &$config, array $action, $key, $position)
    {
        foreach ($action[$key] as $parent) {
            if (array_key_exists($parent, $config)) {
                $offset = self::POSITION_PREPEND === $action[$position] ? 0 : count($config[$parent]['fields']);
                array_splice($config[$parent]['fields'], $offset, 0, $action['fields']);
                return true;
            }
        }
        return false;
    }