Yii2的深入学习--自动加载机制，yii2深入学习--_PHP教程

<span>//</span><span> 引入 vendor 中的 autoload.php 文件，会基于 composer 的机制自动加载类</span>
<span>require</span>(__DIR__ . '/../vendor/autoload.php');

<span>//</span><span> 引入 Yii 框架的文件 Yii.php</span>
<span>require</span>(__DIR__ . '/../vendor/yiisoft/yii2/Yii.php');

<?<span>php
</span><span>/*</span><span>*
 * Yii bootstrap file.
 *
 * @link http://www.yiiframework.com/
 * @copyright Copyright (c) 2008 Yii Software LLC
 * @license http://www.yiiframework.com/license/
 </span><span>*/</span>

<span>require</span>(__DIR__ . '/BaseYii.php'<span>);

</span><span>/*</span><span>*
 * Yii is a helper class serving common framework functionalities.
 *
 * It extends from [[\yii\BaseYii]] which provides the actual implementation.
 * By writing your own Yii class, you can customize some functionalities of [[\yii\BaseYii]].
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @since 2.0
 </span><span>*/</span>
<span>class</span> Yii <span>extends</span><span> \yii\BaseYii
{
}

</span><span>/*</span><span>*
 * spl_autoload_register &mdash; 注册给定的函数作为 __autoload 的实现
 *
 * bool spl_autoload_register ([ callable $autoload_function [, bool $throw = true [, bool $prepend = false ]]] )
 *
 * 将函数注册到SPL __autoload函数队列中。如果该队列中的函数尚未激活，则激活它们。
 * 如果在你的程序中已经实现了__autoload()函数，它必须显式注册到__autoload()队列中。
 * 因为 spl_autoload_register()函数会将Zend Engine中的__autoload()函数取代为spl_autoload()或spl_autoload_call()。
 * 如果需要多条 autoload 函数，spl_autoload_register() 满足了此类需求。
 * 它实际上创建了 autoload 函数的队列，按定义时的顺序逐个执行。
 * 相比之下， __autoload() 只可以定义一次。
 *
 * autoload_function
 * 欲注册的自动装载函数。如果没有提供任何参数，则自动注册 autoload 的默认实现函数spl_autoload()。
 *
 * throw
 * 此参数设置了 autoload_function 无法成功注册时， spl_autoload_register()是否抛出异常。
 *
 * prepend
 * 如果是 true，spl_autoload_register() 会添加函数到队列之首，而不是队列尾部。
 *
 * Yii 注册了 Yii 的 autoload 函数，实现自动加载, 其实现在 \yii\BaseYii 中
 </span><span>*/</span><span>
spl_autoload_register([</span>'Yii', 'autoload'], <span>true</span>, <span>true</span><span>);
</span><span>//</span><span> 定义 Yii 核心的 class 的类名与文件地址的 Map</span>
Yii::<span>$classMap</span> = <span>require</span>(__DIR__ . '/classes.php'<span>);
</span><span>//</span><span> 创建 Yii 的依赖注入的容器</span>
Yii::<span>$container</span> = <span>new</span> yii\di\Container();

spl_autoload_register(['Yii', 'autoload'], <span>true</span>, <span>true</span>);

    <span>/*</span><span>*
     * Class autoload loader.
     * This method is invoked automatically when PHP sees an unknown class.
     * The method will attempt to include the class file according to the following procedure:
     *
     * 1. Search in [[classMap]];
     * 2. If the class is namespaced (e.g. `yii\base\Component`), it will attempt
     *    to include the file associated with the corresponding path alias
     *    (e.g. `@yii/base/Component.php`);
     *
     * This autoloader allows loading classes that follow the [PSR-4 standard](http://www.php-fig.org/psr/psr-4/)
     * and have its top-level namespace or sub-namespaces defined as path aliases.
     *
     * Example: When aliases `@yii` and `@yii/bootstrap` are defined, classes in the `yii\bootstrap` namespace
     * will be loaded using the `@yii/bootstrap` alias which points to the directory where bootstrap extension
     * files are installed and all classes from other `yii` namespaces will be loaded from the yii framework directory.
     *
     * Also the [guide section on autoloading](guide:concept-autoloading).
     *
     * @param string $className the fully qualified class name without a leading backslash "\"
     * @throws UnknownClassException if the class does not exist in the class file
     </span><span>*/</span>
    <span>public</span> <span>static</span> <span>function</span> autoload(<span>$className</span><span>)
    {
        </span><span>//</span><span> 自动加载类</span>
        <span>if</span> (<span>isset</span>(<span>static</span>::<span>$classMap</span>[<span>$className</span><span>])) {
            </span><span>//</span><span> 如果 $classMap 中存在该类，就直接使用</span>
            <span>$classFile</span> = <span>static</span>::<span>$classMap</span>[<span>$className</span><span>];
            </span><span>//</span><span> 如果第一个字符串为'@'，就意味着对应的文件地址是别名，就将它转化成真实的文件地址</span>
            <span>if</span> (<span>$classFile</span>[0] === '@'<span>) {
                </span><span>$classFile</span> = <span>static</span>::getAlias(<span>$classFile</span><span>);
            }
        } </span><span>elseif</span> (<span>strpos</span>(<span>$className</span>, '\\') !== <span>false</span><span>) {
            </span><span>//</span><span> 如果存在'\\',就意味着含有 namespace,可以拼成别名，再根据别名获取真实的文件地址</span>
            <span>$classFile</span> = <span>static</span>::getAlias('@' . <span>str_replace</span>('\\', '/', <span>$className</span>) . '.php', <span>false</span><span>);
            </span><span>//</span><span> 没取到真是文件地址或者获取的地址不是一个文件，就返回空</span>
            <span>if</span> (<span>$classFile</span> === <span>false</span> || !<span>is_file</span>(<span>$classFile</span><span>)) {
                </span><span>return</span><span>;
            }
        } </span><span>else</span><span> {
            </span><span>return</span><span>;
        }

        </span><span>//</span><span> 引入该类的文件</span>
        <span>include</span>(<span>$classFile</span><span>);

        </span><span>//</span><span> 如果是调试模式，而且 $className 即不是类，不是接口，也不是 trait，就抛出异常</span>
        <span>if</span> (YII_DEBUG && !<span>class_exists</span>(<span>$className</span>, <span>false</span>) && !<span>interface_exists</span>(<span>$className</span>, <span>false</span>) && !trait_exists(<span>$className</span>, <span>false</span><span>)) {
            </span><span>throw</span> <span>new</span> UnknownClassException("Unable to find '<span>$className</span>' in file: <span>$classFile</span>. Namespace missing?"<span>);
        }
    }</span>

Yii::<span>$classMap</span> =<span> [
    </span>'app/test/Test' => '/var/www/basic/webtest/Test.php'<span>
];</span>