public function getFallbackPageExtensions($file_ext = null)
    {
        if (empty($this->page_extensions)) {
            if (!$file_ext) {
                $file_ext = CONTENT_EXT;
            }

            if ($this->enabled()) {
                $valid_lang_extensions = [];
                foreach ($this->languages as $lang) {
                    $valid_lang_extensions[] = '.' . $lang . $file_ext;
                }

                if ($this->active) {
                    $active_extension = '.' . $this->active . $file_ext;
                    $key = \array_search($active_extension, $valid_lang_extensions, true);

                    // Default behavior is to find any language other than active
                    if ($this->config->get('system.languages.pages_fallback_only')) {
                        $slice = \array_slice($valid_lang_extensions, 0, $key+1);
                        $valid_lang_extensions = array_reverse($slice);
                    } else {
                        unset($valid_lang_extensions[$key]);
                        array_unshift($valid_lang_extensions, $active_extension);
                    }
                }
                $valid_lang_extensions[] = $file_ext;
                $this->page_extensions = $valid_lang_extensions;
            } else {
                $this->page_extensions = (array)$file_ext;
            }
        }

        return $this->page_extensions;
    }