PSR-0 – Autoloading Standard

Autoloading Standard，即自动加载标准。

这是PSR的第一个标准。

注意，该标准已经被标记为Deprecated，即已经废弃。更推荐使用PSR-4。

本文大部分翻译自https://www.php-fig.org/psr/psr-0/

PSR-0标准要求

1.命名空间和类必须遵循以下命名方法 \<Vendor Name>\(<Namespace>\)*<Class Name>
A fully-qualified namespace and class must have the following structure \<Vendor Name>\(<Namespace>\)*<Class Name>
2.每个命名空间必须有一个最高等级的(“Vendor Name”)
Each namespace must have a top-level namespace (“Vendor Name”).
3.每个命名空间可以拥有多个子空间
Each namespace can have as many sub-namespaces as it wishes.
4.加载文件时每个命名空间分隔符都要转化成目录分隔符
Each namespace separator is converted to a DIRECTORY_SEPARATOR when loading from the file system.
5.类名中下划线要转化为目录分隔符，下划线是不代表任何意思的
Each _ character in the CLASS NAME is converted to a DIRECTORY_SEPARATOR. The _ character has no special meaning in the namespace.
6.命名空间和类名都是以.php为后缀的文件
The fully-qualified namespace and class are suffixed with .php when loading from the file system.
7.命名可以使用大小写
Alphabetic characters in vendor names, namespaces, and class names may be of any combination of lower case and upper case.

\Doctrine\Common\IsolatedClassLoader => /path/to/project/lib/vendor/Doctrine/Common/IsolatedClassLoader.php
\Symfony\Core\Request => /path/to/project/lib/vendor/Symfony/Core/Request.php
\Zend\Acl => /path/to/project/lib/vendor/Zend/Acl.php
\Zend\Mail\Message => /path/to/project/lib/vendor/Zend/Mail/Message.php

\namespace\package\Class_Name => /path/to/project/lib/vendor/namespace/package/Class/Name.php
\namespace\package_name\Class_Name => /path/to/project/lib/vendor/namespace/package_name/Class/Name.php

这是一个已经废弃的标准，没什么可说的。