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Superglobals
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PHP Manual

# Predefined Variables

PHP provides a large number of predefined variables to all scripts. The variables represent everything from external variables to built-in environment variables, last error messages to last retrieved headers.

See also the FAQ titled "How does register_globals affect me?"

## Table of Contents

- 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

참조로 볼수 있는것
Superglobals
언어 레퍼런스
PHP Manual