Magento 1.9 Multiselection fields are all empty in the backend configuration

Question

I have a problem with Magento's backend. In Configuration, each multiselection field is empty, all options are no longer available. This problem is only in the configuration. Why?

I've already tried cleaning the cache and doing the reindex.

Any solution? Thank you

This is the situation:

Answer 1

I had the same issue and fold this solution

I looked at my file /httpdocs/app/code/core/Mage/Adminhtml/Block/System/Config

and matched it with original version

I was missing this line 463

here's a bigger chunk of the code to see full view the bolded area was missing from my file. I added it from original and it fixed it.

                if ($method) {
                    if ($fieldType == 'multiselect') {
                        $optionArray = $sourceModel->$method();
                    } else {
                        $optionArray = array();
                        foreach ($sourceModel->$method() as $value => $label) {
                            $optionArray[] = array('label' => $label, 'value' => $value);
                        }
                    }
                }
                else {
                    $optionArray = $sourceModel->toOptionArray($fieldType == 'multiselect');
                }
                $field->setValues($optionArray);
            }
        }
    }
    return $this;
}