So far, I've seen many different naming conventions used for PHP namespaces. Some people use `PascalCase\Just\Like\For\Classes`, some use `underscored\lower_case\names`, some even use the Java convention for package names: `com\domain\project\package`. 

The question is very simple -- can any of these (or other) conventions be called well-established? Why? Are any of them recommended by authorities like Zend or the developers of well-known PHP frameworks?