SuperGobals PHP

PHP provides 9 Super-globals, which are accessible, anywhere in the entire PHP script. Each Super-global is a built-in variable, and has its special meaning and they are

$GLOBALS
$_SERVER
$_REQUEST
$_POST
$_GET
$_FILES
$_ENV
$_COOKIE
$_SESSION

All superglobals are associative array holds information (data) as key-value pair.

$GLOBALS

This super-global, $GLOBALS is used to access global variables in PHP script. It is an associative array, which holds global variable and its value as key-value pair.

<?php
$a = 20;

function getValue(){
  echo $GLOBALS['a'];

}
getValue();

?>

$_SERVER

$_SERVER is a super-global, provides headers, paths, and script locations information. This information is created by web server.

Example

<?php
echo $_SERVER['SERVER_NAME'];
?>

$_SERVER[‘PHP_SELF’]	Returns currently executing script filename
$_SERVER[‘GATEWAY_INTERFACE’]	Server’s Common Gateway Interface (CGI) version currently using
$_SERVER[‘SERVER_ADDR’]	Returns Host Server IP address
$_SERVER[‘SERVER_NAME’]	Returns Host Server name (yourshala.com)
$_SERVER[‘SERVER_SOFTWARE’]	Returns Server identification string
$_SERVER[‘SERVER_PROTOCOL’]	Returns information protocol name and revision
$_SERVER[‘REQUEST_METHOD’]	Page request method i.e. POST or GET, used to access the page
$_SERVER[‘REQUEST_TIME’]	Starting time stamp of page request.
$_SERVER[‘REQUEST_TIME_FLOAT’]	Starting time stamp with microsecond precision, of page request.
$_SERVER[‘QUERY_STRING’]	Returns query string.
$_SERVER[‘HTTP_ACCEPT’]	Returns current request Accept header
$_SERVER[‘HTTP_ACCEPT_CHARSET’]	Returns Accept_Charset header of current request
$_SERVER[‘HTTP_HOST’]	Returns current request, Host header
$_SERVER[‘HTTP_REFERER’]	Returns current page complete or full URL
$_SERVER[‘HTTPS’]	A script queried using secure HTTP protocol
$_SERVER[‘REMOTE_ADDR’]	Returns User’s IP address, from current page is being viewed.
$_SERVER[‘REMOTE_HOST’]	Returns User’s Host address, from current page is being viewed.
$_SERVER[‘REMOTE_PORT’]	Returns User’s Port, from user is connected to web server.
$_SERVER[‘SCRIPT_FILENAME’]	Returns currently executing php script absolute pathname.
$_SERVER[‘SERVER_ADMIN’]	Gives value of SERVER_ADMIN directive of web server configuration file.
$_SERVER[‘SERVER_PORT’]	Web server port number used for communication
$_SERVER[‘SERVER_SIGNATURE’]	Returns server version and virtual host name, added to server-generated pages
$_SERVER[‘PATH_TRANSLATED’]	Returns current script file system based path.
$_SERVER[‘SCRIPT_NAME’]	Returns current script path
$_SERVER[‘SCRIPT_URI’]	Returns current page URI
$_SERVER[‘REMOTE_USER’]	Returns authenticated user.
$_SERVER[‘REQUEST_URI’]	URI used to access web page. e.g. /index.html
$_SERVER[‘DOCUMENT_ROOT’]	Returns current executing script document root directory.

$_REQUEST

This $_REQUEST superglobal contains all $_GET, $_POST and $_COOKIE values or data.

<form method="get">
 <input type="text" id="myname" name="myname"/>
 <input type="submit" value="OK" />

</form>

<?php
if(!empty($_REQUEST["myname"]))
  echo  $_REQUEST["myname"];
?>

$_GET

Allows to get User submitted form data using HTTP GET REQUEST method in the form of query string.

<form method="get">
 <input type="text" id="myname" name="myname"/>
 <input type="submit" value="OK" />

</form>

<?php
if(!empty($_GET["myname"]))
  echo  $_GET["myname"];
?>

$_POST

Allows to get User submitted form data using HTTP POST REQUEST method.

<form method="post">
 <input type="text" id="myname" name="myname"/>
 <input type="submit" value="OK" />

</form>

<?php
if(!empty($_POST["myname"]))
  echo  $_POST["myname"];
?>

$_FILES

Used to Upload file using HTTP POST REQUEST method

$_SESSION

This $_SESSION superglobal holds data and can be accessed in multiple web pages.

Page 1
$_SESSION["username"] = "Vasu";

Page 2
echo $_SESSION["username"];

$_ENV

It provides information of current Environment in which PHP script is executing.

<?php
echo 'username is ' .$_ENV["USER"] . '!';
?>

$_COOKIES

Used to hold and get data via HTTP Cookies.

$_COOKIE["name"] = "Hello";

echo $_COOKIE["name"];