PHP provides a large number of predefined variables or built-in variables to all scripts:
$GLOBALS: References all variables available in global scope.
$_SERVER: Server and execution environment information.
$_GET: HTTP GET variables.
$_POST: HTTP POST variables.
$_FILES: HTTP File Upload variables.
$_REQUEST: HTTP Request variables.
$_SESSION: Session variables.
$_ENV: Environment variables.
$_COOKIE: HTTP Cookies.
These predefined variables in PHP are "superglobals", or automatic global variables,
which means they are available in all scopes throughout a script.
There is no need to do
global $variable; to access them within functions or methods.