Facebook Target Search: Search for ALL ZIP Codes of a City

Question

I am trying to retrieve all the ZIP codes of a country with the specific code:

$result = TargetingSearch::search(
    TargetingSearchTypes::GEOLOCATION,
    null,
    null,
    array(
        'location_types' => array('zip'),
        'country_code' => 'CY'
    ));

I have a problem where the query value should be (the 2nd null)...If I set it to '6', I get all the ZIPs starting with 6.

In my case, I want ALL the ZIP Codes so I set it on null but I get no results.

Does anyone know what I should set to get all the ZIPs?

Thank you in advance.