无法读取环境变量

本文介绍了无法读取环境变量的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我有一个简单的 Symfony 项目，在 composer.json 中使用 "symfony/dotenv": "4.3.*", 并尝试读取一个环境变量.

I have a simple Symfony project, using "symfony/dotenv": "4.3.*", in the composer.json and trying to read in the value of an environment variable.

这是我的命令:

var_dump($_ENV['MY_NEW_VAR']);

这是我的.env文件

MY_NEW_VAR=testing

执行命令后，我得到以下内容

Upon executing the command I get the following

string(7) "testing"

到目前为止一切都很好......但是现在如果我想使用环境变量来覆盖设置它会返回一个错误.首先我设置环境变量

All good so far.... But now if I want to use environment variables to override the setting it returns an error. First I set the environment variable

export MY_NEW_VAR="something_else"

然后再次执行命令，结果如下

Then execute the command again, with the following results

[ErrorException] Notice: Undefined index: MY_NEW_VAR

如果我使用 unset MY_NEW_VAR 删除环境变量并再次执行命令，我会从 .env 文件中获取值

If I remove the environment variable using unset MY_NEW_VAR and execute the command again I get the value from the .env file

我希望环境变量覆盖 .env 设置，如 .env 文件的注释中所述

I would expect the environment variable to override the .env setting as explained in the comments of the .env file

# In all environments, the following files are loaded if they exist, # the later taking precedence over the former: # # * .env contains default values for the environment variables needed by the app # * .env.local uncommitted file with local overrides # * .env.$APP_ENV committed environment-specific defaults # * .env.$APP_ENV.local uncommitted environment-specific overrides # # Real environment variables win over .env files.

为什么它不适用于环境变量?我错过了什么吗?

Why does it not work with environment variables? Am I missing something?

推荐答案

您问题中的代码是正确的，所以我打赌问题出在其他地方.

The code in your question is correct, so I'd wager the problem lies somewhere else.

getenv()、$_ENV 和 $_SERVER 的工作方式有很多变幻莫测和不一致的地方.根据我的经验，我发现 $_SERVER 更可靠，而且很多时候同时检查两者更安全.例如.如果您检查 Symfony 4.3 的 config/bootstrap.php 上的代码，您将看到如下内容:

There are many vagaries and inconsistencies about how getenv(), $_ENV and $_SERVER work. I have found $_SERVER to be more reliable in my experience, and many times it safer to check both. E.g. if you check the code on config/bootstrap.php for Symfony 4.3 you'll see stuff like this:

$_SERVER['APP_ENV'] = $_ENV['APP_ENV'] = ($_SERVER['APP_ENV'] ?? $_ENV['APP_ENV'] ?? null) ?: 'dev';

无论如何，如果您的 $_ENV 超全局变量最初是空的，那可能是因为 variables_order 设置.检查其值，如果不包含 E，请将其添加到现有值中，并正确填充它.

In any case, if your $_ENV superglobal is initially empty, it could be because on the variables_order setting. Check its value, and if doesn't include an E, prepend it to the existing value and with that it should be populated correctly.

文档 说S 等价于 ES...

在 CGI 和 FastCGI SAPI 中，$_SERVER 也由环境中的值填充；无论 E 在该指令中的其他位置放置如何，S 始终等同于 ES.

In both the CGI and FastCGI SAPIs, $_SERVER is also populated by values from the environment; S is always equivalent to ES regardless of the placement of E elsewhere in this directive.

但我没有发现它一直如此.

but I have not found it to be consistently so.