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Request #63008 Need reliable way of listing environment variables.
Submitted: 2012-09-04 08:17 UTC Modified: 2018-07-07 16:48 UTC
Avg. Score:4.0 ± 0.0
Reproduced:1 of 1 (100.0%)
Same Version:1 (100.0%)
Same OS:1 (100.0%)
From: phpbugs at addiks dot de Assigned: cmb (profile)
Status: Closed Package: *General Issues
PHP Version: 5.4.6 OS: Ubuntu/Debian
Private report: No CVE-ID: None
 [2012-09-04 08:17 UTC] phpbugs at addiks dot de
Hello there,

Currently there are only two ways of accessing environment-variables: a) Using the getenv function, which allows you to access single previous known environment variables, and b) using $_ENV, which is only filled when the php.ini-directive 'variables_order' does contain an 'E', which is sometimes not the case (on my machine that is default).

What i need is a method to list the environment variables no matter what php.ini directives are set (unless access to environment-variables is not explicit denied).

This is needed for things like error-handling for storing the state of the environment to late better understand what is going on or environment-handling in unit-testing. When you cannot list all environment variables, you can never be sure that some variables will hide from you and ruin your testing. 

Access (even write-access) to data which you cannot get a complete overview from is just a crippled concept to me which needs to be fixed. Implementing such a feature should not be too hard.

Test script:

 * Such a function should exists in PHP.
 * (The assertion is always true.
 *  It should work regardless of variables_order.)
 * @return array
function listenv(){
  assert("substr_count(ini_get('variables_order'), 'E')>0;");
  return array_keys($_ENV);

foreach(listenv() as $key){
  $value = var_export(getenv($key), true);
  echo "\${$key} = {$value};\n";

Expected result:
$SHELL = '/bin/bash';
$TERM = 'xterm';
$USER = 'root';
$SUDO_USER = 'username';
$SUDO_UID = '1000';
$USERNAME = 'root';
$MAIL = '/var/mail/root';
$PATH = '/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin';
$LC_COLLATE = 'de_DE.UTF-8';
$PWD = '/home/username';
$LANG = 'de_DE.UTF-8';
$SHLVL = '1';
$SUDO_COMMAND = '/bin/su';
$HOME = '/root';
$LANGUAGE = 'de:en';
$LOGNAME = 'root';
$LC_CTYPE = 'de_DE.UTF-8';
$LESSOPEN = '| /usr/bin/lesspipe %s';
$SUDO_GID = '1003';
$DISPLAY = ':0';
$LESSCLOSE = '/usr/bin/lesspipe %s %s';
$XAUTHORITY = '/home/username/.Xauthority';
$COLORTERM = 'gnome-terminal';
$_ = '/usr/bin/php';

Actual result:
PHP Warning:  assert(): Assertion "substr_count(ini_get('variables_order'), 'E')>0;" failed in /home/gerrit/test.php on line 10
PHP Stack trace:
PHP   1. {main}() /home/username/test.php:0
PHP   2. listenv() /home/username/test.php:14
PHP   3. assert('substr_count(ini_get(\'variables_order\'), \'E\')>0;') /home/username/test.php:10
root@username:/home/username# php -r "var_dump(ini_get('variables_order'));"
string(4) "GPCS"
root@username:/home/username# # this is default-configuration.


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 [2012-09-04 08:32 UTC] phpbugs at addiks dot de
There _would_ be also a third way of accessing environment-variables, accessing '/proc/self/environ'. But that is not possible on most systems because when using PHP as apache2-module the process gets spawned as root and setuid'd to the apache-user, which leads to non-readable '/proc/self/*' files. Maybe there can be something done in that direction?
 [2012-09-04 09:04 UTC]
For your use-case it doesn't sound like performance is an issue so you could just 
do $env = shell_exec("env");
It is also technically available via phpinfo(INFO_ENVIRONMENT) although that 
outputs it with html tags, so you would have to ob-parse it.
 [2012-09-04 09:42 UTC] phpbugs at addiks dot de
Problem with shell_exec is that it only works as long as program-execution is allowed, so this can also not really be considered reliable. Some people disable program-execution on productive servers for security reason, and prompt them to allow program-execution just to read environment-vars does not sound like the way to go.

Reading the environment-variables from phpinfo would be a possible way i have not considered yet. That might work for now, but it sounds more like a dirty workaround. I dont think that phpinfo() was designed to fetch the environment-variables to your application on a regular basis. Who can guarantee that there will always be a phpinfo providing env-var's and that the way it does never change? (I dont like writing software with expiration-date.)

My opinion that there should be a 'listenv' like function to reliable list environment-variables has not changed.
 [2018-07-07 16:48 UTC]
-Status: Open +Status: Closed -Assigned To: +Assigned To: cmb
 [2018-07-07 16:48 UTC]
As of PHP 7.1.0 getenv() can be called without argument to yield
an associative array of all environment variables.
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