Home php教程 php手册 PHP 5.3中的命名空间使用方法浅述

PHP 5.3中的命名空间使用方法浅述

Jun 13, 2016 am 11:03 AM
name php Instructions name characteristic of space important

PHP 5.3 的一个新的重要特性就是 命名空间(namespace)。

这一特性在 PHP5.0x 时候就提出过,后来被取消并安排在 PHP6 中实现。而此次又再次“提前”到了 PHP 5.3 发布,可见开发人员对其的重视以及谨慎的态度。

官方发布时说明文档的内容可能已过期(documentation maybe out dated),所以在这里简单的说明命名空间的用法:首先是声明一个命名空间,加入了新的关键字 namespace ,其应在类文件的开头

<ol class="dp-c">
<li class="alt"><span><span><?php  </SPAN></span><li class=""><span>namespace Project::Module;   </span></li>
<li class="alt"><span> </span></li>
<li class="">
<span></span><span class="keyword"><strong><font color="#006699">class</font></strong></span><span> User {  </span>
</li></span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">const</font></strong></span><span> STATUS_OK = true;  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">function</font></strong></span><span> register(</span><span class="vars"><font color="#dd0000">$data</font></span><span>) {  </span>
</li>
<li class=""><span>...  </span></li>
<li class="alt"><span>}  </span></li>
<li class=""><span> </span></li>
<li class="alt"><span>...  </span></li>
<li class=""><span>}  </span></li>
</ol>
Copy after login

然后在控制器中(可能是其他文件)就可以这样调用

<ol class="dp-c">
<li class="alt"><span><span class="vars"><font color="#dd0000">$user</font></span><span> = </span><span class="keyword"><strong><font color="#006699">new</font></strong></span><span> Project::Module::User();   </span></span></li>
<li class="">
<span></span><span class="vars"><font color="#dd0000">$user</font></span><span>->register(</span><span class="vars"><font color="#dd0000">$register_info</font></span><span>); </span>
</li>
</ol>
Copy after login

的确与平常的并无两样,但是我们可以将两个相互独立的类联系起来。比如

<ol class="dp-c">
<li class="alt"><span><span>Project::Module::User;   </span></span></li>
<li class=""><span>Project::Module::Blog;  </span></li>
</ol>
Copy after login

这样就能从语言本身更容易描述和理解变量、类之间的关系,从而避免了“传统”上的 Project_Module_Blog 这样冗长的命名方式。

上面的说明可能很难说明使用命名空间带来了什么好处,新增加的 use 和 as 关键字或许能更好的说明问题。use 和 as 语句可以引用和声明 命名空间的“别名”。比如,上述的控制器中实例化类的代码可以这样写

<ol class="dp-c">
<li class="alt"><span><span class="keyword"><strong><font color="#006699">use</font></strong></span><span> Project::Module;  </span></span></li>
<li class="">
<span></span><span class="vars"><font color="#dd0000">$user</font></span><span> = </span><span class="keyword"><strong><font color="#006699">new</font></strong></span><span> Module::User();   </span>
</li>
<li class="alt">
<span></span><span class="vars"><font color="#dd0000">$user</font></span><span>->register(</span><span class="vars"><font color="#dd0000">$register_info</font></span><span>);  </span>
</li>
</ol>
Copy after login

甚至

<ol class="dp-c">
<li class="alt"><span><span class="keyword"><strong><font color="#006699">use</font></strong></span><span> Project::Module::User </span><span class="keyword"><strong><font color="#006699">as</font></strong></span><span> ModuleUser;  </span></span></li>
<li class="">
<span></span><span class="vars"><font color="#dd0000">$user</font></span><span> = </span><span class="keyword"><strong><font color="#006699">new</font></strong></span><span> ModuleUser;   </span>
</li>
<li class="alt">
<span></span><span class="vars"><font color="#dd0000">$user</font></span><span>->register(</span><span class="vars"><font color="#dd0000">$register_info</font></span><span>);  </span>
</li>
</ol>
Copy after login

类中的常量也可以通过命名空间访问,比如上述类中的 STATUS_OK 就可以通过命名空间

<ol class="dp-c"><li class="alt"><span><span>Project::Module::User::STATUS_OK  </span></span></li></ol>
Copy after login

访问。进一步的,也可以用别名简化那么长的“变量名称”

<ol class="dp-c">
<li class="alt"><span><span class="keyword"><strong><font color="#006699">use</font></strong></span><span> Project::Module::User::STATUS_OK </span><span class="keyword"><strong><font color="#006699">as</font></strong></span><span> STATUS_OK;  </span></span></li>
<li class="">
<span></span><span class="func">echo</span><span> STATUS_OK;  </span>
</li>
</ol>
Copy after login

顺便提下“超空间(The Global Namespace)”的概念。所谓的“超空间”,就是没有指定命名空间的变量、类和函数。比如

<ol class="dp-c">
<li class="alt"><span><span class="keyword"><strong><font color="#006699">function</font></strong></span><span> foo() {  </span></span></li>
<li class=""><span>...  </span></li>
<li class="alt"><span>}  </span></li>
</ol>
Copy after login

这的函数,可以使用 foo() 执行的同时,也可以使用 ::foo(); 这样执行。

最后,配合使用 autoload 函数即可载入指定命名空间的类。简单的函数如下

<ol class="dp-c">
<li class="alt"><span><span class="keyword"><strong><font color="#006699">function</font></strong></span><span> __autoload( </span><span class="vars"><font color="#dd0000">$classname</font></span><span> ) {  </span></span></li>
<li class="">
<span></span><span class="vars"><font color="#dd0000">$classname</font></span><span> = </span><span class="func">strtolower</span><span>( </span><span class="vars"><font color="#dd0000">$classname</font></span><span> );  </span>
</li>
<li class="alt">
<span></span><span class="vars"><font color="#dd0000">$classname</font></span><span> = </span><span class="func">str_replace</span><span>( </span><span class="string"><font color="#0000ff">'::'</font></span><span>, DIRECTORY_SEPARATOR, </span><span class="vars"><font color="#dd0000">$classname</font></span><span> );  </span>
</li>
<li class="">
<span></span><span class="keyword"><strong><font color="#006699">require_once</font></strong></span><span>( dirname( </span><span class="keyword"><strong><font color="#006699">__FILE__</font></strong></span><span> ) . </span><span class="string"><font color="#0000ff">'/'</font></span><span> . </span><span class="vars"><font color="#dd0000">$classname</font></span><span> . </span><span class="string"><font color="#0000ff">'.class.php'</font></span><span> );  </span>
</li>
<li class="alt"><span>}  </span></li>
</ol>
Copy after login

这样,比如调用

<ol class="dp-c"><li class="alt"><span><span>__autoload(</span><span class="string"><font color="#0000ff">'Project::Module::User'</font></span><span>);  </span></span></li></ol>
Copy after login

就可以自动载入 Project_Module_User.class.php 文件(虽然这样看起来并不方便多少)。


Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

PHP 8.4 Installation and Upgrade guide for Ubuntu and Debian PHP 8.4 Installation and Upgrade guide for Ubuntu and Debian Dec 24, 2024 pm 04:42 PM

PHP 8.4 brings several new features, security improvements, and performance improvements with healthy amounts of feature deprecations and removals. This guide explains how to install PHP 8.4 or upgrade to PHP 8.4 on Ubuntu, Debian, or their derivati

7 PHP Functions I Regret I Didn't Know Before 7 PHP Functions I Regret I Didn't Know Before Nov 13, 2024 am 09:42 AM

If you are an experienced PHP developer, you might have the feeling that you’ve been there and done that already.You have developed a significant number of applications, debugged millions of lines of code, and tweaked a bunch of scripts to achieve op

How To Set Up Visual Studio Code (VS Code) for PHP Development How To Set Up Visual Studio Code (VS Code) for PHP Development Dec 20, 2024 am 11:31 AM

Visual Studio Code, also known as VS Code, is a free source code editor — or integrated development environment (IDE) — available for all major operating systems. With a large collection of extensions for many programming languages, VS Code can be c

Explain JSON Web Tokens (JWT) and their use case in PHP APIs. Explain JSON Web Tokens (JWT) and their use case in PHP APIs. Apr 05, 2025 am 12:04 AM

JWT is an open standard based on JSON, used to securely transmit information between parties, mainly for identity authentication and information exchange. 1. JWT consists of three parts: Header, Payload and Signature. 2. The working principle of JWT includes three steps: generating JWT, verifying JWT and parsing Payload. 3. When using JWT for authentication in PHP, JWT can be generated and verified, and user role and permission information can be included in advanced usage. 4. Common errors include signature verification failure, token expiration, and payload oversized. Debugging skills include using debugging tools and logging. 5. Performance optimization and best practices include using appropriate signature algorithms, setting validity periods reasonably,

How do you parse and process HTML/XML in PHP? How do you parse and process HTML/XML in PHP? Feb 07, 2025 am 11:57 AM

This tutorial demonstrates how to efficiently process XML documents using PHP. XML (eXtensible Markup Language) is a versatile text-based markup language designed for both human readability and machine parsing. It's commonly used for data storage an

PHP Program to Count Vowels in a String PHP Program to Count Vowels in a String Feb 07, 2025 pm 12:12 PM

A string is a sequence of characters, including letters, numbers, and symbols. This tutorial will learn how to calculate the number of vowels in a given string in PHP using different methods. The vowels in English are a, e, i, o, u, and they can be uppercase or lowercase. What is a vowel? Vowels are alphabetic characters that represent a specific pronunciation. There are five vowels in English, including uppercase and lowercase: a, e, i, o, u Example 1 Input: String = "Tutorialspoint" Output: 6 explain The vowels in the string "Tutorialspoint" are u, o, i, a, o, i. There are 6 yuan in total

Explain late static binding in PHP (static::). Explain late static binding in PHP (static::). Apr 03, 2025 am 12:04 AM

Static binding (static::) implements late static binding (LSB) in PHP, allowing calling classes to be referenced in static contexts rather than defining classes. 1) The parsing process is performed at runtime, 2) Look up the call class in the inheritance relationship, 3) It may bring performance overhead.

What are PHP magic methods (__construct, __destruct, __call, __get, __set, etc.) and provide use cases? What are PHP magic methods (__construct, __destruct, __call, __get, __set, etc.) and provide use cases? Apr 03, 2025 am 12:03 AM

What are the magic methods of PHP? PHP's magic methods include: 1.\_\_construct, used to initialize objects; 2.\_\_destruct, used to clean up resources; 3.\_\_call, handle non-existent method calls; 4.\_\_get, implement dynamic attribute access; 5.\_\_set, implement dynamic attribute settings. These methods are automatically called in certain situations, improving code flexibility and efficiency.

See all articles