Description:
------------
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:
---------------
<?php

/**
 * 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_MESSAGES = 'de_DE.UTF-8';
$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.