DĂ©finition des espaces de noms

(PHP 5 >= 5.3.0, PHP 7, PHP 8)

Bien que du code PHP valide puisse ĂȘtre contenu dans un espace de noms, seuls les types de code suivants peuvent ĂȘtre affectĂ©s par les espaces de noms : les classes (incluant les abstraites, les traits et les enums), les interfaces, les fonctions et les constantes.

Les espaces de noms sont déclarés avec le mot-clé namespace. Un fichier contenant un espace de noms doit déclarer l'espace au début du fichier, avant tout autre code, avec une seule exception : le mot clé declare.

Exemple #1 DĂ©claration d'un espace de noms

<?php
namespace MonProjet;

const CONNEXION_OK = 1;
class Connexion { /* ... */ }
function connecte() { /* ... */ }

Note: Les noms complÚtement qualifiés (c.-à-d. les noms commençant avec un antislash) ne sont pas autorisés dans les déclarations d'espaces de noms, car de telles constructions sont interprétées comme des expressions d'espace de noms relatif.

Le seul élément autorisé avant la déclaration d'espace de noms est la commande declare, pour définir l'encodage du fichier source. De plus, aucun code non-PHP ne peut précéder la déclaration d'espace de noms, y compris des espaces :

Exemple #2 Erreur de déclaration d'un espace de noms

<html>
<?php
namespace MonProjet; // erreur fatale : le namespace doit ĂȘtre le premier Ă©lĂ©ment du script

De plus, contrairement Ă  d'autres structures PHP, le mĂȘme espace de noms peut ĂȘtre dĂ©fini dans plusieurs fichiers, ce qui permet de scinder le contenu d'un espace de noms sur plusieurs fichiers.

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User Contributed Notes 10 notes

up
211
kuzawinski dot marcin at NOSPAM dot gmail dot com ¶
11 years ago
If your code looks like this:

<?php
    namespace NS;
?>

...and you still get "Namespace declaration statement has to be the very first statement in the script" Fatal error, then you probably use UTF-8 encoding (which is good) with Byte Order Mark, aka BOM (which is bad). Try to convert your files to "UTF-8 without BOM", and it should be ok.
up
143
danbettles at yahoo dot co dot uk ¶
17 years ago
Regarding constants defined with define() inside namespaces...

define() will define constants exactly as specified.  So, if you want to define a constant in a namespace, you will need to specify the namespace in your call to define(), even if you're calling define() from within a namespace.  The following examples will make it clear.

The following code will define the constant "MESSAGE" in the global namespace (i.e. "\MESSAGE").

<?php
namespace test;
define('MESSAGE', 'Hello world!');
?>

The following code will define two constants in the "test" namespace.

<?php
namespace test;
define('test\HELLO', 'Hello world!');
define(__NAMESPACE__ . '\GOODBYE', 'Goodbye cruel world!');
?>
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81
FatBat ¶
12 years ago
Expanding on @danbettles note, it is better to always be explicit about which constant to use.

<?php
    namespace NS;

    define(__NAMESPACE__ .'\foo','111');
    define('foo','222');

    echo foo;  // 111.
    echo \foo;  // 222.
    echo \NS\foo  // 111.
    echo NS\foo  // fatal error. assumes \NS\NS\foo.
?>
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65
huskyr at gmail dot com ¶
16 years ago
"A file containing a namespace must declare the namespace at the top of the file before any other code"

It might be obvious, but this means that you *can* include comments and white spaces before the namespace keyword.

<?php
// Lots 
// of
// interesting
// comments and white space

namespace Foo;
class Bar {
}
?>
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48
jeremeamia at gmail dot com ¶
16 years ago
You should not try to create namespaces that use PHP keywords. These will cause parse errors. 

Examples:

<?php
namespace Project/Classes/Function; // Causes parse errors
namespace Project/Abstract/Factory; // Causes parse errors
?>
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8
anisgazig at gmail dot com ¶
5 years ago
namespace statement  is defined at first of the php files. But 
    before namespace declaration only three elements allowed.
      1.declare statement
      2.spaces
      3.comments
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7
Anonymous ¶
18 years ago
@ RS: Also, you can specify how your __autoload() function looks for the files. That way another users namespace classes cannot overwrite yours unless they replace your file specifically.
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2
Baptiste ¶
18 years ago
There is nothing wrong with PHP namespaces, except that those 2 instructions give a false impression of package management.
... while they just correspond to the "with()" instruction of Javascript.

By contrast, a package is a namespace for its members, but it offers more (like deployment facilities), and a compiler knows exactly what classes are in a package, and where to find them.
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-1
anisgazig at gmail dot com ¶
5 years ago
Namespace name are case-insensitive.
namespace App
and
namespace app
are same meaning.

Besides, Namespace keword are case-insensitive.
Namespace App
namespace App
and
NAMESPACE App
are same meaning.
up
-1
dino at tuxweb dot it ¶
3 years ago
Please note that a PHP Namespace declaration cannot start with a number.
It took some time for me to debug...
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