About predefined global variables in PHP

One thing that makes PHP so flexible and easy to use is that it has several predefined variables which are global and accessible from whichever PHP script you write.

Here is a complete list of them:

• Superglobals — Superglobals are built-in variables that are always available in all scopes
• $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
• $php_errormsg — The previous error message
• $HTTP_RAW_POST_DATA — Raw POST data
• $http_response_header — HTTP response headers
• $argc — The number of arguments passed to script
• $argv — Array of arguments passed to script

You can get a full reference of them on this page superglobals
The most commonly used are these: $GLOBALS, $_POST, $_GET, $_REQUEST, $_COOKIE, $_SERVER and $_FILES. So I will explain these in different posts and show some examples.