Declaring sub-namespaces
Using namespaces: Basics
Namespaces
PHP Manual

## Defining multiple namespaces in the same file

Multiple namespaces may also be declared in the same file. There are two allowed syntaxes.

Example #1 Declaring multiple namespaces, simple combination syntax

`<?php
namespace MyProject;
const CONNECT_OK = 1;
class Connection { /* ... */ }
function connect() { /* ... */ }
namespace AnotherProject;
const CONNECT_OK = 1;
class Connection { /* ... */ }
function connect() { /* ... */ }
?>`

This syntax is not recommended for combining namespaces into a single file. Instead it is recommended to use the alternate bracketed syntax.

Example #2 Declaring multiple namespaces, bracketed syntax

`<?php
namespace MyProject {
const CONNECT_OK = 1;
class Connection { /* ... */ }
function connect() { /* ... */ }
}
namespace AnotherProject {
const CONNECT_OK = 1;
class Connection { /* ... */ }
function connect() { /* ... */ }
}
?>`

It is strongly discouraged as a coding practice to combine multiple namespaces into the same file. The primary use case is to combine multiple PHP scripts into the same file.

To combine global non-namespaced code with namespaced code, only bracketed syntax is supported. Global code should be encased in a namespace statement with no namespace name as in:

Example #3 Declaring multiple namespaces and unnamespaced code

`<?php
namespace MyProject {
const CONNECT_OK = 1;
class Connection { /* ... */ }
function connect() { /* ... */ }
}
namespace { // global code
session_start();
$a = MyProject\connect();
echo MyProject\Connection::start();
}
?>`

No PHP code may exist outside of the namespace brackets except for an opening declare statement.

Example #4 Declaring multiple namespaces and unnamespaced code

`<?php
declare(encoding='UTF-8');
namespace MyProject {
const CONNECT_OK = 1;
class Connection { /* ... */ }
function connect() { /* ... */ }
}
namespace { // global code
session_start();
$a = MyProject\connect();
echo MyProject\Connection::start();
}
?>`