Defining namespaces
Defining multiple namespaces in the same file
Namespaces
PHP Manual

## Declaring sub-namespaces

(PHP 5 >= 5.3.0)

Much like directories and files, PHP namespaces also contain the ability to specify a hierarchy of namespace names. Thus, a namespace name can be defined with sub-levels:

Example #1 Declaring a single namespace with hierarchy

`<?php
namespace MyProject\Sub\Level;
const CONNECT_OK = 1;
class Connection { /* ... */ }
function connect() { /* ... */ }
?>`
The above example creates constant MyProject\Sub\Level\CONNECT_OK, class MyProject\Sub\Level\Connection and function MyProject\Sub\Level\connect.

Defining namespaces
Defining multiple namespaces in the same file
Namespaces
PHP Manual