How to Define Namespaces in PHP?

[SKREECH]

Hi friends,
Since I am new to the PHP programming language I don't have enough knowledge about it. I want to know about the namespaces that are used in PHP. So, thought that posting here would be helpful. Please tell me how to Define Namespaces in PHP? Any other details regarding the namespaces would also be of great help. Hoping the needful help sooner.!!

[Praetor]

Declaring a namespace in PHP is very simple. You have to declare the namespace by using the 'namespace' keyword. If you are familiar with the C# and Java programming languages, then you can understand quickly. By using the namespaces you can change the structure of PHP applications for the better. Namespace allows the developer to seperate their code into modules or groups which inturn makes the code easier to read. A file containing a namespace must declare the namespace at the top of the file before any other code.

[kelfro]

Namespaced code is defined using a single namespace keyword at the top of your PHP file. It must be the first command and it should not contain non-PHP code, HTML, or white-space can precede the command. Also as said before that namespace must declared at the top before any other code. This should pass one exception which is the declare keyword. The only code construct allowed before a namespace declaration is the declare statement, for defining encoding of a source file. The advantage of using the namespaces are that they prevent class and function name conflicts, it allows you to have numerous classes with the same name, as long as they are in different namespaces.

[absolute55]

You can declare a single namespace with the declare exception. You can have a look at the following coding which demonstrates the same :

<?php
namespace MyExample;

const CONNECT_OK = 1;
class Connection { /* ... */ }
function connect() { /* ... */  }

?>

[Reegan]

While knowing about the namespaces, you should also know about the Sub-namespaces. In PHP, you can define a hierarchy of namespaces so libraries can be sub-divided. You will have to use backslash (\) for separating the sub-namespaces. Just check the example so that you can understand more clearly.

• MyExample\SubName
• MyExample\Database\MySQL
• CompanyName\MyExample\Library\Common\Widget1

Hope that this post was somewhat useful for you.!!

[Viensterrr]

The following example can explain you more properly. So have a glance at the following example :
coding of myExample.php

namspace lib;

class myExample
{

public function call()
{
echo 'hello world';
}

} 

And the following is the coding of index.php :

require 'lib/myExample.php';

$bar = new myExample();

$bar = new lib\myExample();
$bar->call();
use lib\myExample;

$bar = new myExample();
$bar->call();

use lib\myExample as newName;

$bar = new newName();
$bar->call();