getenv

Gets the value of an environment variable.

You can see a list of all the environmental variables by using phpinfo(). Many of these variables are listed within » RFC 3875, specifically section 4.1, "Request Meta-Variables".

The variable name.

Returns the value of the environment variable varname, or FALSE if the environment variable varname does not exist.

<?php
// Example use of getenv()
$ip = getenv('REMOTE_ADDR');

// Or simply use a Superglobal ($_SERVER or $_ENV)
$ip = $_SERVER['REMOTE_ADDR'];
?>

putenv() -

apache_getenv() -

Superglobals -