(PHP 5 >= 5.3.0, PHP 7)
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();
$a = MyProject\connect();
echo MyProject\Connection::start();
}
?>
"use" statements are required to be placed after the "namespace my\space" but before the "{".
e.g.
<?php
namespace foo\bar;
use my\space\MyClass;
{
// place code here
} // end of namespace foo\bar
namespace another\bar;
use my\space\MyClass;
use my\space\AnotherClass;
{
// place code here
} // end of namespace another\bar
?>
<?php
// You cannot mix bracketed namespace declarations with unbracketed namespace declarations - will result in a Fatal error
namespace a;
echo "I belong to namespace a";
namespace b {
echo "I'm from namespace b";
}
using of global namespaces and multiple namespaces in one PHP file increase the complexity and decrease readability of the code.
Let's try not use this scheme even it's very necessary (although there is not)
<?php
//Namespace can be used in this way also
namespace MyProject {
function connect() { echo "ONE"; }
Sub\Level\connect();
}
namespace MyProject\Sub {
function connect() { echo "TWO"; }
Level\connect();
}
namespace MyProject\Sub\Level {
function connect() { echo "THREE"; }
\MyProject\Sub\Level\connect(); // OR we can use this as below
connect();
}
//call same named function using namespace
//food.php
<?php
namespace Food;
require ('Apple.php');
require('Orange.php');
use Apples;
use Oranges;
Apples\eat();
Oranges\eat();
?>
//Apple.php
<?php
namespace Apples;
function eat()
{
echo "eat apple";
}
?>
//Orange.php
<?php
namespace Oranges;
function eat()
{
echo "eat Orange";
}
?>
Be careful with include combined to namespaces:
file b.php
<?php
const WHERE_I_AM = 'I am in B';
function i_am_in() {
\A\cr_echo(WHERE_I_AM);
}
?>
file c.php
<?php
namespace C {
const WHERE_I_AM = 'I am in C';
function i_am_in() {
\A\cr_echo(WHERE_I_AM);
}
}
?>
main file
<?php
namespace A {
const CR = "\r\n";
const WHERE_I_AM = 'I am in A';
function cr_echo($msg) {
echo $msg . CR;
}
function i_am_in() {
cr_echo(WHERE_I_AM);
}
}
namespace B {
require 'b.php';
}
namespace {
require 'c.php';
\A\i_am_in(); //ok
\B\i_am_in(); // fatal-error
\C\i_am_in(); //ok
}
?>
Notice it's not allowed to mix bracketed namespace with unbracketed namespace declarations.
<?php
namespace MyTest;
const TEST = 777;
//in this way
echo \MyTest\TEST . '<br />';
//Or this way
echo TEST . '<br />';
namespace AnotherTest {
const TEST = 555;
echo \AnotherTest\TEST . '<br />';
echo \MyTest\TEST;
}
?>
This code will issue a fatal error, like this: Fatal error: Cannot mix bracketed namespace declarations with unbracketed namespace declarations in C:\xampp\htdocs\teste2.php on line 11.
last two examples give:
Fatal error: Call to undefined method MyProject\Connection::start() in Z:\home\test1.ru\www\link.php on line 12
