public function getTreeCache($table, $key): ?array
    {
        $filename = $table.'_'.$key.'.php';

        if (file_exists($this->cacheDir.'/'.$filename)) {
            self::$cache[$table.'_'.$key] = (include $this->cacheDir.'/'.$filename);
        }

        return self::$cache[$table.'_'.$key] ?? null;
    }