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 5 >= 5.3.0, PHP 7, PHP 8)
Es können auch mehrere Namespaces in derselben Datei definiert werden. Es gibt hierfür zwei mögliche Schreibweisen:
Beispiel #1 Mehrere Namespaces definieren, einfache Kombinationssyntax
<?php
namespace MyProject;
const CONNECT_OK = 1;
class Connection { /* ... */ }
function connect() { /* ... */ }
namespace AnotherProject;
const CONNECT_OK = 1;
class Connection { /* ... */ }
function connect() { /* ... */ }
?>Diese Syntax ist nicht die empfohlene Syntax, um mehrere Namespaces in einer einzigen Datei zusammenzuführen. Stattdessen wird die geklammerte Syntax empfohlen.
Beispiel #2 Mehrere Namespaces definieren, geklammerte Syntax
<?php
namespace MyProject {
const CONNECT_OK = 1;
class Connection { /* ... */ }
function connect() { /* ... */ }
}
namespace AnotherProject {
const CONNECT_OK = 1;
class Connection { /* ... */ }
function connect() { /* ... */ }
}
?>Es wird stark von der Programmierpraxis, mehrere Namespaces in einer Datei zu definieren, abgeraten. Der wichtigste Einsatzzweck dieser Möglichkeit ist es, mehrere PHP-Skripte in derselben Datei zusammenzuführen.
Um Code ohne Namensräume mit solchem mit Namensräumen zusammenzuführen, wird nur die geklammerte Syntax unterstützt. Globaler Code sollte in einem Namespace-Statement ohne Namespace eingeschlossen werden:
Beispiel #3 Mehrere Namespaces und Code ohne Namespace deklarieren
<?php
namespace MyProject {
const CONNECT_OK = 1;
class Connection { /* ... */ }
function connect() { /* ... */ }
}
namespace { // global code
session_start();
$a = MyProject\connect();
echo MyProject\Connection::start();
}
?>Es darf kein PHP-Code außerhalb der Namespace-Klammern existieren, abgesehen von einem beginnenden declare-Ausdruck.
Beispiel #4 Mehrere Namespaces und Code ohne Namespace deklarieren
<?php
declare(encoding='UTF-8');
namespace MyProject {
const CONNECT_OK = 1;
class Connection { /* ... */ }
function connect() { /* ... */ }
}
namespace { // globaler Code
session_start();
$a = MyProject\connect();
echo MyProject\Connection::start();
}
?>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
// 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";
}<?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();
}If you have the habit to always use the closing PHP tag "?>" in your test files, remember that with the bracketed syntax code outside the brackets, including new lines outside the PHP tags, is not allowed. In particular, even though PHP sees a new line after the closing tag as a part of the line and eats it, some editors, such as Gedit, Gvim, Vim and Nano in Ubuntu, will add yet another new line after this new line and this will create an error.//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";
}
?>There are rational examples of where the ability to blend multiple namespaces into a single file is not only desirable but also absolutely necessary. An example of where this ability is useful is over in the very popular phpseclib library where they are PSR-4 compliant but, in order to be compliant, they have to read a directory of files to know what classes are available so that the autoloader can load the correct files. If they, instead, just bundled the defaults into one file using this mechanism already supported by PHP core, there would be no need to do extraneous scanning of the file system.
That's just one legitimate use-case where strict compliance with PSRs gets in the way of good software development.