A superglobal is a predefined variable that is always accessible, regardless of scope. You can access the PHP superglobals through any function, class, or file.
PHP’s superglobal variables are $_SERVER, $GLOBALS, $_REQUEST, $_POST, $_GET, $_FILES, $_ENV, $_COOKIE, $_SESSION.
$_SERVER is an array that includes information such as headers, paths, and script locations. The entries in this array are created by the web server.
$_SERVER[‘SCRIPT_NAME’] returns the path of the current script:
<?php echo $_SERVER['SCRIPT_NAME']; //Outputs "/test.php" ?>