Pimcore\Model\Object\Service::getOptionsForSelectField PHP Method

    public static function getOptionsForSelectField($object, $fieldname)
    {
        $class = null;
        $options = [];
        if (is_object($object) && method_exists($object, "getClass")) {
            $class = $object->getClass();
        } elseif (is_string($object)) {
            $object = "\\" . ltrim($object, "\\");
            $object = new $object();
            $class = $object->getClass();
        }
        if ($class) {
            /**
             * @var ClassDefinition\Data\Select $definition
             */
            $definition = $class->getFielddefinition($fieldname);
            if ($definition instanceof ClassDefinition\Data\Select || $definition instanceof ClassDefinition\Data\Multiselect) {
                $_options = $definition->getOptions();
                foreach ($_options as $option) {
                    $options[$option["value"]] = $option["key"];
                }
            }
        }
        return $options;
    }