A PHP site uses an XML file as a configuration class.
```php
TemplateDirectory . " " );
*/
```
Explanation of the translation:
1. The original Chinese comments are translated into English while preserving their meaning.
2. The code structure and syntax are kept intact, ensuring that the PHP code remains functional.
3. The example provided (`$c = new Configuration('config.xml');`) is explained in the comment as a way to demonstrate how to use the `Configuration` class for reading site configurations from an XML file.