PHP Superglobals

PHP provides a special set of predefined global arrays containing various useful nuggets of information. These arrays are known as superglobals because they’re accessible from anywhere in your script — including inside functions — and you don’t need to declare them as global using the global keyword.

Here’s a full list of the superglobals available in PHP, as of version 5.3:

$GLOBALS    Contains a list of all global variables in the script (excluding superglobals)

$_GET       Holds a list of all form fields sent by the browser using the GET request

$_POST      Holds a list of all form fields sent by the browser using the POST request

$_COOKIE    holds a list of all cookies sent by the browser

$_REQUEST   Contains all the keys and values in the $_GET, $_POST and $_COOKIE arrays combined

$_FILES     holds a list of any files uploaded by the browser

$_SESSION   allows you to store and retrieve persistent session variables for the current browser

$_SERVER    Holds server environment info such as the filename of the running script, and the IP address of the browser.

$_ENV       contains a list of environment variables passed to PHP. These can include variables provided by the shell, as well as CGI variables.

For example, we can use the $_GET superglobal to retrieve a value included in the query string of the script’s URL, and display the value in the page:

<?php

$yourName = $_GET['yourName'];
echo "Hello, $yourName!";

?>

If you run the above script using a URL along the lines of  http://www.example.com/script.php?yourName=Fred    then the script displays: