private function _createFile($dir, $name, $ext)
    {
        if (!empty($this->rootDir)) {
            if (!file_exists($this->_getFileDir($dir))) {
                mkdir($this->_getFileDir($dir), 0777, true);
            }
            if (!file_exists($this->_getFilePath($dir, $name, $ext))) {
                if (file_put_contents($this->_getFilePath($dir, $name, $ext), '') === false) {
                    throw new \Exception("Could not create $ext for {$this->username}.");
                }
            }
        }
    }