命名空间与自动加载系列(三)--命名空间的使用

作者: 温新

分类: 【PHP基础】

阅读: 1471

时间: 2021-05-17 11:23:29

前面了解了如何声明命名空间，那么接下来就是学习怎么使用命名空间。在了解命名空间之前，先来了解一下如何打一个文件，我这里以Linux系统为例，访问文件有三种方式：

文件位置：/home/ziruchu/test.txt；/home/ziruchu/config/url.txt

  • 绝对路径名形式。如 cat /home/ziruchu/test.txt

  • 相对路径名形式

    <span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(0, 0, 0)">cd</span> <span style="box-sizing: border-box;color: rgb(152, 26, 26)">/</span><span style="box-sizing: border-box;color: rgb(0, 0, 0)">home</span><span style="box-sizing: border-box;color: rgb(152, 26, 26)">/</span><span style="box-sizing: border-box;color: rgb(0, 0, 0)">ziruchu</span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(0, 0, 0)">cat</span> <span style="box-sizing: border-box;color: rgb(0, 0, 0)">cat</span> <span style="box-sizing: border-box;color: rgb(0, 0, 0)">config</span><span style="box-sizing: border-box;color: rgb(152, 26, 26)">/</span><span style="box-sizing: border-box;color: rgb(0, 0, 0)">conf</span>.<span style="box-sizing: border-box;color: rgb(0, 0, 0)">txt</span></span>

    cat config/conf.txt表示相对于当前目录，也可以写成cat ./config/conf.txt

  • 相对文件名形式。如cat test.txt，也可以写成cat ./test.txt

与文件系统访问一样，PHP 命名空间中的元素使用同样的原理。例如，类名可以通过三种方式引用：

  • 非限定名称。
  • 限定名称。
  • 完全限定名称。

下面用案例进行演示，新建目录 为laravel项目，其包含三个文件，如下：

文件位置：laravel/index.php、laravel/Post.php、Post.php

为每个文件添加内容：

<span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(170, 85, 0)">// Post.php</span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(152, 26, 26)"><?</span><span style="box-sizing: border-box;color: rgb(0, 0, 0)">php</span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(119, 0, 136)">namespace</span> <span style="box-sizing: border-box;color: rgb(0, 0, 255)">App\Controller</span>;</span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(119, 0, 136)">class</span> <span style="box-sizing: border-box;color: rgb(0, 0, 255)">Post</span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px">{</span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"> <span style="box-sizing: border-box;color: rgb(119, 0, 136)">public</span> <span style="box-sizing: border-box;color: rgb(119, 0, 136)">static</span> <span style="box-sizing: border-box;color: rgb(119, 0, 136)">function</span> <span style="box-sizing: border-box;color: rgb(0, 0, 255)">index</span>()</span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"> {</span><br></br><span style="box-sizing: border-box;padding-right: 0.1px">  <span style="box-sizing: border-box;color: rgb(119, 0, 136)">echo</span> <span style="box-sizing: border-box;color: rgb(34, 17, 153)">__METHOD__</span> . <span style="box-sizing: border-box;color: rgb(0, 0, 0)">PHP_EOL</span>;</span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"> }</span><br></br><span style="box-sizing: border-box;padding-right: 0.1px">}</span>

<span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(170, 85, 0)">// Common.php</span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(152, 26, 26)"><?</span><span style="box-sizing: border-box;color: rgb(0, 0, 0)">php</span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(119, 0, 136)">namespace</span> <span style="box-sizing: border-box;color: rgb(0, 0, 255)">Common</span>;</span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(119, 0, 136)">class</span> <span style="box-sizing: border-box;color: rgb(0, 0, 255)">Common</span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px">{</span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"> <span style="box-sizing: border-box;color: rgb(119, 0, 136)">public</span> <span style="box-sizing: border-box;color: rgb(119, 0, 136)">static</span> <span style="box-sizing: border-box;color: rgb(119, 0, 136)">function</span> <span style="box-sizing: border-box;color: rgb(0, 0, 255)">index</span>()</span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"> {</span><br></br><span style="box-sizing: border-box;padding-right: 0.1px">  <span style="box-sizing: border-box;color: rgb(119, 0, 136)">echo</span> <span style="box-sizing: border-box;color: rgb(34, 17, 153)">__METHOD__</span> . <span style="box-sizing: border-box;color: rgb(0, 0, 0)">PHP_EOL</span>;</span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"> }</span><br></br><span style="box-sizing: border-box;padding-right: 0.1px">}</span>

<span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(170, 85, 0)">// index.php</span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(152, 26, 26)"><?</span><span style="box-sizing: border-box;color: rgb(0, 0, 0)">php</span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(119, 0, 136)">namespace</span> <span style="box-sizing: border-box;color: rgb(0, 0, 255)">App</span>;</span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(119, 0, 136)">class</span> <span style="box-sizing: border-box;color: rgb(0, 0, 255)">Index</span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px">{</span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"> <span style="box-sizing: border-box;color: rgb(119, 0, 136)">public</span> <span style="box-sizing: border-box;color: rgb(119, 0, 136)">static</span> <span style="box-sizing: border-box;color: rgb(119, 0, 136)">function</span> <span style="box-sizing: border-box;color: rgb(0, 0, 255)">index</span>() </span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"> {</span><br></br><span style="box-sizing: border-box;padding-right: 0.1px">  <span style="box-sizing: border-box;color: rgb(119, 0, 136)">echo</span> <span style="box-sizing: border-box;color: rgb(34, 17, 153)">__METHOD__</span> . <span style="box-sizing: border-box;color: rgb(0, 0, 0)">PHP_EOL</span>;</span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"> }</span><br></br><span style="box-sizing: border-box;padding-right: 0.1px">}</span>

Post.php与index.php在同一根（App）命名空间中，Common.php自成一根（Common）命名空间。

非限定名称的使用

index.php文件中，我们来访问根命名空间下index.php文件中的index方法。

<span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(170, 85, 0)">// index.php</span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(152, 26, 26)"><?</span><span style="box-sizing: border-box;color: rgb(0, 0, 0)">php</span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(170, 85, 0)">// 省略重复内容，新增如下内容</span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px">    </span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(0, 0, 0)">index</span>::<span style="box-sizing: border-box;color: rgb(0, 0, 0)">index</span>(); <span style="box-sizing: border-box;color: rgb(170, 85, 0)">// 输出App\Index::index</span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box"></span></span>

使用非限定名称index::index访问时，会自动到App命名空间中寻找index类中的index方法。

简单地说，也就是当前命名空间中寻找该类的方法。

限定名称的使用

<span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(170, 85, 0)">// index.php</span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(119, 0, 136)">include</span> <span style="box-sizing: border-box;color: rgb(170, 17, 17)">'./Post.php'</span>;</span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(119, 0, 136)">include</span> <span style="box-sizing: border-box;color: rgb(170, 17, 17)">'./Common.php'</span>;</span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(0, 0, 0)">Controller\Post</span>::<span style="box-sizing: border-box;color: rgb(0, 0, 0)">index</span>(); <span style="box-sizing: border-box;color: rgb(170, 85, 0)">// 输出 App\Controller\Post::index</span></span>

同理，当使用Controller\Post::index()访问时，会自动为其添加上App。简单地说，还是到当前命名空间下去寻找。

完全限定名称的使用

<span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(170, 85, 0)">// index.php</span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(119, 0, 136)">include</span> <span style="box-sizing: border-box;color: rgb(170, 17, 17)">'./Post.php'</span>;</span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(119, 0, 136)">include</span> <span style="box-sizing: border-box;color: rgb(170, 17, 17)">'./Common.php'</span>;</span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(0, 0, 0)">\Common\Common</span>::<span style="box-sizing: border-box;color: rgb(0, 0, 0)">index</span>();</span>

这里需要的注意的是，Common与App是同一级的命名空间。现在换成windows下的目录来理解，如laravel目录下有两下目录，分别是app与common。

请登录后再评论