PHP - Manual: getenv

2024-11-14

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getenv

(PHP 4, PHP 5, PHP 7, PHP 8)

getenv — 获取一个环境变量的值

说明

getenv(string $varname, bool $local_only = false): string

getenv(): array

获取一个环境变量的值。

使用 phpinfo() 你可以看到所有环境变量的列表。这些变量很多都在 » RFC 3875 的范围之内，尤其是章节4.1，"Request Meta-Variables"。

参数

varname: 变量名。
local_only: 设置为 true 以仅返回本地环境变量（由操作系统或 putenv() 设置）。

返回值

返回环境变量 varname 的值，如果环境变量 varname 不存在则返回 false。如果省略 varname，则所有环境变量都将作为关联数组 array 返回。

更新日志

版本	说明
7.1.0	现在可以省略 `varname` 来检索所有环境变量的关联数组 array。
5.5.38, 5.6.24, 7.0.9	添加 `local_only` 参数。

注释

警告

如果 PHP 在诸如 Fast CGI 之类的 SAPI 中运行，则此函数将始终返回由 SAPI 设置的环境变量的值，即使已使用 putenv() 来设置同名的本地环境变量。使用 local_only 参数返回本地设置的环境变量的值。

范例

示例 #1 getenv() 例子


<?php
// getenv() 使用示例
$ip = getenv('REMOTE_ADDR');

// 或简单仅使用全局变量（$_SERVER 或 $_ENV）
$ip = $_SERVER['REMOTE_ADDR'];

// 安全地获取环境变量，忽略通过 SAPI 或 putenv 修改的值
$ip = getenv('REMOTE_ADDR', true) ?: getenv('REMOTE_ADDR')
?>

参见

putenv() - 设置环境变量的值
apache_getenv() - 获取 Apache subprocess_env 变量
超全局变量

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User Contributed Notes 15 notes

down

Anonymous ¶

4 years ago


Contrary to what eng.mrkto.com said, getenv() isn't always case-insensitive. On Linux it is not:

<?php
var_dump(getenv('path')); // bool(false)
var_dump(getenv('Path')); // bool(false)
var_dump(getenv('PATH')); // string(13) "/usr/bin:/bin"

down

jcastromail at yahoo dot es ¶

1 year ago


I did a benchmark about env.

constants : 
0.00067687034606934 ms
getenv : 
0.056761026382446 ms

(less is better)

https://github.com/eftec/php-benchmarks#define--const--env

And, in Windows at leat, reading the env value is considerably slow (in comparison with a constant), so PHP doesn't cache the information and asks to the OS the env value per call.

So, if you are calling once per request, then there is not a problem. However, if you are calling it many times per request, then it could affects the performance.

down

eng.mrkto.com ¶

11 years ago


This function is useful (compared to $_SERVER, $_ENV) because it searches $varname key in those array case-insensitive manner.
For example on Windows $_SERVER['Path'] is like you see Capitalized, not 'PATH' as you expected.
So just: <?php getenv('path') ?>

down

php at keith tyler dot com ¶

10 years ago


All of the notes and examples so far have been strictly CGI.
It should not be understated the usefulness of getenv()/putenv() in CLI as well.

You can pass a number of variables to a CLI script via environment variables, either in Unix/Linux bash/sh with the "VAR='foo'; export $VAR" paradigm, or in Windows with the "set VAR='foo'" paradigm. (Csh users, you're on your own!) getenv("VAR") will retrieve that value from the environment.

We have a system by which we include a file full of putenv() statements storing configuration values that can apply to many different CLI PHP programs. But if we want to override these values, we can use the shell's (or calling application, such as ant) environment variable setting method to do so.

This saves us from having to manage an unmanageable amount of one-off configuration changes per execution via command line arguments; instead we just set the appropriate env var first.

down

yw()beeznest!com ¶

5 years ago


As noted on httpoxy.org, getenv() can confuse you in having you believe that all variables come from a "safe" environment (not all of them do).

In particular, $_SERVER['HTTP_PROXY'] (or its equivalent getenv('HTTP_PROXY')) can be manually set in the HTTP request header, so it should not be considered safe in a CGI environment.

In short, try to avoid using getenv('HTTP_PROXY') without properly filtering it.

down

larby dot robert at gmail dot com ¶

3 years ago


From PHP 7.1 => getenv() no longer requires its parameter. If the parameter is omitted, then the current environment variables will be returned as an associative array.

Source: http://php.net/manual/en/migration71.changed-functions.php

down

kyong ¶

18 years ago


As you know, getenv('DOCUMENT_ROOT') is useful.
However, under CLI environment(I tend to do quick check
if it works or not), it doesn't work without modified php.ini
file. So I add "export DOCUMENT_ROOT=~" in my .bash_profile.

down

pritisn at gmail dot com ¶

7 years ago


for quick check of getenv() adding a new env variable -
if you add a new env variable, make sure not only apache but xampp is also restarted.
Otherwise getenv() will return false for the newly added env variable.

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hello at jabran dot me ¶

7 years ago


Beware that when using this function with PHP built-in server – i.e. php -S localhost:8000 – it will return boolean FALSE.

down

Anonymous ¶

3 years ago


It is worth noting that since getenv('MY_VARIABLE') will return false when the variable given is not set, there is no direct way to distinguish between a variable that is unset and one that is explicitly set to the value bool(false) when using getenv().  
This makes it somewhat tricky to have boolean environment variables default to true if unset, which you can work around either by using "falsy" values such as 0 with the strict comparison operators or by using the superglobal arrays and isset().

down

sam at sambarrow dot com ¶

14 years ago


SERVER_NAME is the name defined in the apache configuration.
HTTP_HOST is the host header sent by the client when using the more recent versions of the http protocol.

down

-1

chuck dot reeves at gmail dot com ¶

12 years ago


When writing CLI applications, not that any environment variables that are set in your web server config will not be passed through.  PHP will pass through system environment variables that are prefixed based off the safe_mode_allowed_env_vars directive in your php.ini

down

-14

jaraco at jaraco dot com ¶

4 years ago


The example on how to fallback produces a syntax error on PHP 5.2:

-bash-3.2$ cat test.php
<?php

$ip = getenv('REMOTE_ADDR', true) ?: getenv('REMOTE_ADDR')

?>

-bash-3.2$ /web/cgi-bin/php5 test.php 
Content-type: text/html

<br />
<b>Parse error</b>:  syntax error, unexpected ':' in <b>/home/content/25/11223125/test.php</b> on line <b>3</b><br />

On PHP 5.2, one must write

$ip = getenv('REMOTE_ADDR', true) ? getenv('REMOTE_ADDR', true) : getenv('REMOTE_ADDR')

down

-43

f dot hartmann2 at gmx dot net ¶

12 years ago


A function returning the remote adress of the visiting browser could look like this:


<?php

function getIPfromXForwarded() {

    $ipString=@getenv("HTTP_X_FORWARDED_FOR");

    $addr = explode(",",$ipString);

    return $addr[sizeof($addr)-1];

}

?>



Note that some adresses are followed by a whitespace and ip2long(getIPfromXForwarded()) would not return the expected result.


Make use of trim() in your scripts, either in the function itself, or the surrounding space of the caller.


Greetings

down

-50

renko at <remove>virtual-life dot net ¶

17 years ago


The function 'getenv' does not work if your Server API is ASAPI (IIS).

So, try to don't use getenv('REMOTE_ADDR'), but $_SERVER["REMOTE_ADDR"].

add a note

官方地址：https://www.php.net/manual/en/function.getenv.php

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PHP官方手册 - 互联网笔记

getenv

说明

参数

返回值

更新日志

注释

范例

参见

User Contributed Notes 15 notes