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A Twist In Namespaces

by: PHP Builder Staff
|
August 28, 2009

A New Revolution in PHP
With PHP5.3--which is in itself a precursor and somewhat of a teaser for PHP 6--comes something rather new to PHP: Namespaces. As object-oriented developers well know, the point of object-oriented development is to remove ambiguity from development and data access items. What this actually requires is finding common functionality and implementing them in a reusable framework--usually as classes. However, even the widest scope implementation will eventually start running into issues with naming conventions. This is where namespaces really shines.
PHP has been a while in the making though. Probably what seperates PHP from other languages like C# and Java is that PHP has evolved. We all know that the original version of PHP (then called Personal Home Pages) was released in 1995 by Rasmus Lerdorf. By the time PHP reached version 3 it was already an extremely powerful procedural Programming language. PHP4 introduced rudementory OOP implementations, PHP5 represents a rather stable and concise OOP model. Now PHP 5.3 implements Namespaces.
Critics of PHP will argue that the language is a mess: function names are inconsistent (strpos(), str_split(), substr()), object handling has been tacked on, and some of the syntax is very bizarre when compared to the conventions of other languages. However, PHP is one of the most-used programming languages there are. The reason: versatility. Virtually anyone, without much training, can start to use PHP in a simple procedural form, and PHP written 10 years ago in PHP3 will most likely work on PHP5.3 without a major rewrite. PHP development is rapid if not elegant or structured: it is rarely pretty or structured, yet it is readable in a way that very few other languages are.
Figure out the how
Unlike other OOP languages, PHP has to retain compatibility with code that is not namespaced. This means you can choose whether you want to use namespaces or not. However, if you are using PHP5.3 or above, I would recommend always using them, even if you use the same one for your entire project.
By default all class, constant and function names are located in the global space--exactly where they were before the introduction of namespaces. To define Namespace Code, we use a single Namespace keyword at the top of our PHP file. It MUST be the first command (with the exception of declare) and no non-php code, HTML or white-space can precede the command.

<?php
// define this code in the 'ProjectName' namespace
namespace ProjectName;

// ... code ...
?>

The code following this line will be part of the ProjectName namespace.

Sub-namespaces

PHP allows you to define a hierarchy of namespaces so libraries can be sub-divided. Sub-namespaces are separated using a backslash (\) character, e.g.
ProjectName\SubName
ProjectName\Database\MySQL
CompanyName\ProjectName\Library\Common\Widget1

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