Defining namespaces
(PHP 5 >= 5.3.0, PHP 7, PHP 8)
Although any valid PHP code can be contained within a namespace, only the following types of code are affected by namespaces: classes (including abstracts and traits), interfaces, functions and constants.
Namespaces are declared using the namespace
keyword. A file containing a namespace must declare the namespace
at the top of the file before any other code - with one exception: the
declare keyword.
Example #1 Declaring a single namespace
<?php
namespace MyProject;
const CONNECT_OK = 1;
class Connection { /* ... */ }
function connect() { /* ... */ }
?>
The only code construct allowed before a namespace declaration is theNote: Fully qualified names (i.e. names starting with a backslash) are not allowed in namespace declarations, because such constructs are interpreted as relative namespace expressions.
declare statement, for defining encoding of a source file. In addition,
no non-PHP code may precede a namespace declaration, including extra whitespace:
Example #2 Declaring a single namespace
<html>
<?php
namespace MyProject; // fatal error - namespace must be the first statement in the script
?>
In addition, unlike any other PHP construct, the same namespace may be defined in multiple files, allowing splitting up of a namespace's contents across the filesystem.
