PHP Manual

Namespace definition

The namespace is declared using namespace keyword, which should be at the very beginning of the file. Example:

Example #1 Defining namespace

    namespace MyProject

Connection /* ... */ }
connect() { /* ... */  }
Same namespace name can be used in multiple files.

Namespace can contain class, constant and function definitions, but no free code.

Namespace definition does the following:

See also the full name resolution rules.

PHP Manual