PHP命名空间和自动加载初探，php命名空间初探

PHP命名空间和自动加载初探，php命名空间初探

参考资料： PHP手册-语言参考：http://php.net/manual/zh/language.namespaces.php   概要： 1. 声明了命名空间之后，下面的const, function, class都会划归到该命名空间。 2. 只有声明过命名空间的PHP 文件才能加载有命名空间的PHP文件。 3. PHP 5.3 及以上才能使用命名空间     名词：     关键字：namespace 用来声明 本PHP文件的命名空间     常量：__NAMESPACE__ 用来返回当前命名空间的名称 默认为空字符串
    操作符： use 默认以最后一个\后的字符串为别名，配合 as 则为 as后的字符串，与MySQL的字段别名一致。   实际操作如下： 在apache目录下建立如下文件：index.php,Order.php,User.php     Order.php 的内容为    

<span> 1</span> <?<span>php
</span><span> 2</span> <span>/*</span><span>*
</span><span> 3</span> <span> * @Author: Martin
</span><span> 4</span> <span> * @Support: Martin
</span><span> 5</span> <span> * @Last Modified by:   Martin
</span><span> 6</span>  <span>*/</span>
<span> 7</span> <span>namespace Order;
</span><span> 8</span> 
<span> 9</span> <span>const</span> STR = 'order list<br />'<span>;
</span><span>10</span> 
<span>11</span> <span>function</span><span> detail()
</span><span>12</span> <span>{
</span><span>13</span>     <span>return</span> 'order detail<br />'<span>;
</span><span>14</span> <span>}
</span><span>15</span> <span>function</span><span> call_by_self()
</span><span>16</span> <span>{
</span><span>17</span>     <span>return</span> 'call by self<br />'<span>;
</span><span>18</span> <span>}
</span><span>19</span> <span>/*</span><span>*
</span><span>20</span> <span> *
</span><span>21</span>  <span>*/</span>
<span>22</span> <span>class</span><span> Orderlist
</span><span>23</span> <span>{
</span><span>24</span> 
<span>25</span>     <span>public</span> <span>function</span><span> __construct()
</span><span>26</span> <span>    {
</span><span>27</span>         <span>echo</span> 'Class NameSpace is "', __NAMESPACE__, '"'<span>;
</span><span>28</span> <span>    }
</span><span>29</span>     <span>public</span> <span>function</span><span> show_list()
</span><span>30</span> <span>    {
</span><span>31</span>         <span>for</span> (<span>$i</span> = 0; <span>$i</span> < 5; <span>$i</span>++<span>) {
</span><span>32</span>             <span>echo</span> "<ul><li>this is order<span>$i</span><br />"<span>;
</span><span>33</span>             <span>//</span><span>内部直接访问</span>
<span>34</span>             <span>echo</span><span> detail();
</span><span>35</span>             <span>echo</span> "</li></ul>"<span>;
</span><span>36</span> <span>        }
</span><span>37</span> <span>    }
</span><span>38</span> <span>}
</span><span>39</span> <span>//</span><span>内部通过命名空间访问</span>
<span>40</span> <span>echo</span> \Order\call_by_self();

 

index.php 内容为：

<span> 1</span> <?<span>php
</span><span> 2</span> <span>/*</span><span>*
</span><span> 3</span> <span> * @Author: Martin
</span><span> 4</span> <span> * @Support: Martin
</span><span> 5</span> <span> * @Last Modified by:   Martin
</span><span> 6</span>  <span>*/</span>
<span> 7</span> <span>namespace index;
</span><span> 8</span> <span>include_once</span>('Order.php'<span>);
</span><span> 9</span> 
<span>10</span> <span>//</span><span>外部访问class 实例化即可使用</span>
<span>11</span> <span>use</span><span> Order\Orderlist;
</span><span>12</span> <span>$orderlist</span> = <span>new</span><span> orderlist;
</span><span>13</span> <span>$orderlist</span>-><span>show_list();
</span><span>14</span> 
<span>15</span> <span>//</span><span>外部访问静态变量和function 直接访问</span>
<span>16</span> <span>use</span><span> Order;
</span><span>17</span> <span>echo</span><span> Order\STR;
</span><span>18</span> <span>echo</span> Order\detail();

 

打印结果为：

以上内容包含了：通过命名空间来访问文件和直接实例化访问，以及本空间直接访问。 命名空间的存在是为了防止两个同名的class都被载入，使用命名空间在加载第三方的类时能避免同名冲突。   下面来说一下自动加载   SPL 的全称是：Standard PHP Library PHP标准库，在PHP5以后已经内置在PHP中，无需另外安装。 SPL包含了一套针对数据结构、迭代器、异常、文件处理等的函数库。   自动装载库有以下函数 spl_autoload_call：尝试调用所有已注册的__autoload()函数来装载请求类

 

User.php 内容为：

<span>1</span> <span>namespace User;
</span><span>2</span> <span>//</span><span>直接载入Order</span>
<span>3</span> <span>#</span><span>include('Order.php');
</span><span>4</span> <span>//自动载入</span>
<span>5</span> spl_autoload_register(<span>function</span>(<span>$className</span><span>) {
</span><span>6</span>     <span>var_dump</span>(<span>$className</span><span>);
</span><span>7</span> <span>});
</span><span>8</span> spl_autoload_call('Order');

 

打印结果为：

 

SPL自动载入函数包含如下：

spl_autoload_extensions： 注册并返回spl_autoload函数使用的默认文件扩展名。
get_include_path： 设置默认引用的文件夹
spl_autoload_register： 自动引入文件
  实际操作如下： 我们重新调整目录结构和并复制order 到 lib下面 如下：

 

修改User.php 如下：

<span> 1</span> <span>namespace User;
</span><span> 2</span> 
<span> 3</span> <span>//</span><span>直接载入Order</span>
<span> 4</span> <span>#</span><span>include('Order.php');
</span><span> 5</span> <span>//自动载入</span>
<span> 6</span> <span>define</span>('LIB_DIR', __DIR__ . DIRECTORY_SEPARATOR . 'lib' .<span> DIRECTORY_SEPARATOR);
</span><span> 7</span> spl_autoload_register(<span>function</span> (<span>$class</span><span>) {
</span><span> 8</span>     <span>$path</span> = LIB_DIR . <span>$class</span> . '.lib.php'<span>;
</span><span> 9</span>     <span>include</span> (<span>$path</span><span>);
</span><span>10</span> <span>});
</span><span>11</span> 
<span>12</span> spl_autoload_call('Order'<span>);
</span><span>13</span> <span>use</span><span> Order;
</span><span>14</span> 
<span>15</span> <span>$orderList</span> = <span>new</span><span> \Order\Orderlist();
</span><span>16</span> <span>$orderList</span>->show_list();

 

打印结果为：

 

注意： 当采用SPL载入文件时，use并不能触发spl_autoload_register函数，他会被new触发，这样就会提示找不到文件， 所有采用spl_autoload_call 来提前触发自动载入。   本文地址：http://www.cnblogs.com/martin-tan/p/4864539.html  问题： 使用get_include_path，spl_autoload_extensions并且spl_autoload_register默认为空的情况下并不能直接载入目录下的文件，原因如上。（？）