Variables that you can access from any part of your code is called global variable. In Php, you can not create global variable but PHP use some variable that act like as super global variable.
There are some superglobal variables
$_ENV[]:-This is an array that contains environment variables.
<?php
print_r($_ENV);
?>
$_GET[]:- This is an array and holds all of the GET variables gathered from the user’s web browser.
<?php
print_r($_GET);
?>
$_POST[] – This is an array and holds all of the POST variables gathered from the user’s web browser.
<?php
print_r($_POST);
?>
$_SERVER[] – This kind of array holds the values of web-server variables.
<?php
print_r($_SERVER)
?>
It will show all web server variables value like HTTP_HOST, HTTP_CONNECTION, etc.