PHP Superglobals: Global Variables

Superglobals were introduced in PHP 4.1.0. They are built-in variables that are always available in all scopes. You can access them from any function, class or file without having to do anything special.

The PHP superglobal variables are:

$GLOBALS - Contains all global variables, including other superglobals.
$_SERVER - Contains information about the web server and the request made to it.
$_REQUEST - Contains $_GET, $_POST, and possibly $_COOKIE variables.
$_POST - Contains variables sent via an HTTP POST request.
$_GET - Contains variables sent via an HTTP GET request.
$_FILES - Contains variables sent via an HTTP POST file upload.
$_ENV - Contains all environment variables set by the web server.
$_COOKIE - Contains variables sent via HTTP cookies.
$_SESSION - Contains variables stored in a user's session.

PHP $_SERVER Global Variable

$_SERVER is a PHP super global variable which holds information about the server and the environment. It includes headers, paths, and script locations.

You can use the print_r statement to print the contents of $_SERVER. The pre tags above and below it separates each item out on to a new line, making it easier to read.

<?php
echo '<pre>';
print_r($_SERVER);
echo '</pre>';
?>

$_SERVER['SERVER_ADDR']: Returns the IP address of the host server
$_SERVER['SERVER_NAME']: Returns the name of the host server
$_SERVER['REQUEST_METHOD']: Returns the request method used to access the page
$_SERVER['QUERY_STRING']: Returns the query string if the page is accessed via a query string
$_SERVER['HTTP_HOST']: Returns the Host header from the current request
$_SERVER['HTTPS']: Is the script queried through a secure HTTP protocol
$_SERVER['REMOTE_ADDR']: Returns the IP address from where the user is viewing the current page
$_SERVER['REMOTE_HOST']: Returns the Host name from where the user is viewing the current page
$_SERVER['REMOTE_PORT']: Returns the port being used on the user's machine to communicate with the web server
$_SERVER['SERVER_PORT']: Returns the port on the server machine being used by the web server for communication
$_SERVER['SCRIPT_NAME']: Returns the path of the current script
$_SERVER['SCRIPT_URI']: Returns the URI of the current page