How does PHP handle Environment Variables?
Jul 14, 2025 am 03:01 AMTo access environment variables in PHP, use getenv() or the $_ENV superglobal. 1. getenv('VAR_NAME') retrieves a specific variable. 2. $_ENV['VAR_NAME'] accesses variables if variables_order in php.ini includes "E". Set variables via CLI with VAR=value php script.php, in Apache with SetEnv, in FPM with env[VAR] = value, and in Docker or Laravel via .env files. Common issues include variables not being passed through in CGI/FPM setups, requiring PassEnv or explicit definitions, and ensuring server restarts after config changes. Debug by printing getenv() or checking $_ENV population. Avoid exposing sensitive data via phpinfo() or logs.
PHP handles environment variables in a straightforward way, but how you access them depends on the context—like whether PHP is running as an Apache module, via CLI, or under something like FPM. Here's how it generally works and what you need to know.

How to Access Environment Variables in PHP
You can retrieve environment variables using the getenv()
function or by checking the $_ENV
superglobal array.
-
Using
getenv()
This function returns the value of a specific environment variable:$dbHost = getenv('DB_HOST');
Using
$_ENV
This associative array contains all available environment variables:$dbHost = $_ENV['DB_HOST'];
Note: Whether $_ENV
is populated depends on your variables_order
setting in php.ini. Make sure it includes "E" (like variables_order = "EGPCS"
).

Setting Environment Variables for PHP
How and where you set environment variables depends on how PHP is running.
CLI (Command Line)
You can set them directly when calling the script:DB_HOST=localhost php script.php
Apache (mod_php)
UseSetEnv
in your.htaccess
or Apache config:SetEnv DB_HOST localhost
FPM or FastCGI
In your pool config (e.g.,/etc/php-fpm.d/www.conf
), add:env[DB_HOST] = localhost
Docker / .env files
When using Docker or frameworks like Laravel, environment variables are often loaded from.env
files via tools likevlucas/phpdotenv
.
Common Issues and Gotchas
Sometimes things don’t work as expected because of how PHP gets its environment.
Variables might not be passed through
Especially in CGI/FPM setups, environment variables from the shell might not reach PHP unless explicitly defined.Apache’s
PassEnv
vsSetEnv
If you're using Apache,PassEnv
makes system-level variables available to PHP, whileSetEnv
sets them directly in Apache.Caching or misconfigurations
After changing environment settings, restart PHP or Apache for changes to take effect.Security note
Don't expose sensitive data viaphpinfo()
or log output—it could leak environment variables.
Bonus Tip: Debugging Environment Variables
If you're not seeing the variables you expect, try:
Printing out all available ones:
print_r(getenv());
Checking if
$_ENV
is empty due tovariables_order
misconfiguration.Looking at the server configuration or CLI command used to run the script.
That’s about it—you can read and use environment variables in PHP pretty easily once you understand how they’re being set and passed through your environment.
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