Gets the value of an environment variable.
You can see a list of all the environmental variables by using phpinfo(). You can find out what many of them mean by taking a look at the » CGI specification, specifically the » page on environmental variables.
// Example use of getenv()
$ip = getenv('REMOTE_ADDR');
// Or simply use a Superglobal ($_SERVER or $_ENV)
$ip = $_SERVER['REMOTE_ADDR'];