grzanieplus.pl/plugins/stLanguagePlugin/modules/stLanguageBackend/lib/stModuleWebapi.class.php

<?php

class stLanguageBackendWebApi extends autoStLanguageBackendWebApi
{
    public function GetDefaultLanguage($object)
    {
        stWebApi::getLogin($object->_session_hash, 'webapi_read');

        $result = new stdClass();
        $result->language = stSimpleLanguageHelper::cultureToShortcut(stLanguage::getOptLanguage());

        return $result;
    }
}