PHP : Web Basics - [8.21] Reading Environment Variables

8.21.1 Problem

You want to get the value of an environment variable.

8.21.2 Solution

Read the value from the $_ENV superglobal array:

$name = $_ENV['USER'];

8.21.3 Discussion

Environment variables are named values associated with a process. For instance, in Unix, you can check the value of $_ENV['HOME'] to find the home directory of a user:

print $_ENV['HOME']; // user's home directory
/home/adam

Early versions of PHP automatically created PHP variables for all environment variables by default. As of 4.1.0, php.ini-recommended disables this because of speed considerations; however php.ini-dist continues to enable environment variable loading for backward compatibility.

The $_ENV array is created only if the value of the variables_order configuration directive contains E. If $_ENV isn't available, use getenv( ) to retrieve an environment variable:

$path = getenv('PATH');

The getenv( ) function isn't available if you're running PHP as an ISAPI module.