为什么在 require_once 中包含 __DIR__? [英] Why include __DIR__ in the require_once?

问题描述

例如，我总是看到这样的自动加载器:

For example, I always see autoloaders called like this:

require_once __DIR__ . '/../vendor/autoload.php';

那个和更简洁的有什么区别

What is the difference between that and the more concise

require_once '../vendor/autoload.php';

?

推荐答案

PHP 脚本相对于当前路径(getcwd() 的结果)运行，而不是相对于它们自己文件的路径.使用 __DIR__ 强制包含相对于它们自己的路径发生.

PHP scripts run relative to the current path (result of getcwd()), not to the path of their own file. Using __DIR__ forces the include to happen relative to their own path.

为了演示，创建以下文件(和目录):

To demonstrate, create the following files (and directories):

- file1.php
- dir/
   - file2.php
   - file3.php

如果 file2.php 包含 file3.php 像这样:

If file2.php includes file3.php like this:

include `file3.php`.

如果你直接调用file2.php，它会工作得很好.但是，如果 file1.php includes file2.php，则当前目录 (getcwd()) 将是file2.php 错误，所以不能包含 file3.php.

It will work fine if you call file2.php directly. However, if file1.php includes file2.php, the current directory (getcwd()), will be wrong for file2.php, so file3.php cannot be included.

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