问题描述
getenv() 和 $_ENV 有什么区别?
使用两者之间有什么权衡吗?
Any trade-offs between using either?
我注意到有时 getenv() 可以满足我的需要，而 $_ENV 却不能(例如 HOME).
I noticed sometimes getenv() gives me what I need, while $_ENV does not (such as HOME).
推荐答案
根据php关于 getenv 的文档，它们完全相同，只是 getenv 在不区分大小写的文件系统(如 Windows)上运行时会以不区分大小写的方式查找变量.在 Linux 主机上，它仍然区分大小写.大多数时候这可能无关紧要，但文档中的一条评论解释道:
According to the php documentation about getenv, they are exactly the same, except that getenv will look for the variable in a case-insensitive manner when running on case-insensitive file systems (like Windows). On Linux hosts it still works as case-sensitive. Most of the time it probably doesn't matter, but one of the comments on the documentation explains:
例如在 Windows 上 $_SERVER['Path'] 就像你看到的那样，第一个字母大写，而不是你可能期望的 'PATH'.
For example on Windows $_SERVER['Path'] is like you see, with the first letter capitalized, not 'PATH' as you might expect.
因此，我可能会选择使用 getenv 来改善跨平台行为，除非您确定要检索的环境变量的大小写.
Because of that, I would probably opt to use getenv to improve cross-platform behavior, unless you are certain about the casing of the environment variable you are trying to retrieve.
Steve Clay 在此答案中的评论突出了另一个区别:
Steve Clay's comment in this answer highlights another difference:
新增getenv() 优点:访问前无需检查isset/empty.getenv() 不会发出通知.
Added
getenv()advantage: you don't need to checkisset/emptybefore access.getenv()won't emit notices.
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