PHP Tutorial - PHP Super globals

The superglobals are available throughout your script. Superglobals include form data sent from your visitor, cookie data, session information, local server information, and more.

PHP superglobal

There are nine superglobal arrays available shown in the following table.

Variable	Meaning
$_GET	Contains all variables sent via a HTTP GET request. For example, a URL of myfile.php?name=Paul would load myfile.php and give you $_GET["name"] with the value "Paul".
$_POST	Contains all variables sent via a HTTP POST request.
$_FILES	Contains all variables sent via a HTTP POST file upload.
$_COOKIE	Contains all variables sent via HTTP cookies.
$_REQUEST	Contains all variables sent via HTTP GET, HTTP POST, and HTTP cookies. This is the equivalent of combining $_GET, $_POST, and $_COOKIE.
$_SESSION	Contains all variables stored in a user's session.
$_SERVER	Contains all variables set by the web server.
$_ENV	Contains all environment variables.
$GLOBALS	An array containing all global variables in your script.

Key value for $_ENV and $_SERVER

The most commonly used $_SERVER variables are shown in the following table. Only PHP_SELF is available on the command line.

Name	Value
HTTP_REFERER	If the user clicked a link to get the current page, this will contain the URL of the previous page, or it will be empty if the user entered the URL directly.
HTTP_USER_AGENT	The name reported by the visitor's web browser.
PATH_INFO	Any data passed in the URL after the script name.
PHP_SELF	The name of the current script.
REQUEST_METHOD	Either GET or POST.
QUERY_STRING	Includes everything after the question mark in a GET request. Not available on the command line.

Example - Use $_SERVER

HTTP_REFERER and HTTP_USER_AGENT can find out a lot about your visitor and then take the appropriate action.

For example:

<?php 
        if (isset($_SERVER['HTTP_REFERER'])) { 
                print "The page you were on previously was {$_SERVER['HTTP_REFERER']}<br />"; 
        } else { 
                print "You didn't click any links to get here<br />"; 
        } 
?> 
<a href="refer.php">Click me!</a>

The code above generates the following result.

The PATH_INFO element in $_SERVER allows you to grab directory information specified after the script. Consider this script:

<?PHP
if (isset($_SERVER['PATH_INFO'])) { 
        print "The page you requested was {$_SERVER['PATH_INFO']}<br />"; 
} else { 
        print "You didn't request a page<br />"; 
} 
?>

The code above generates the following result.

Save the code above as pathinfo.php, then load it in your web browser. Edit the URL, adding a file name to the end of pathinfo.php. Such as, yoursite.com/pathinfo.php/path/file.txt. Load the page to see extra path information.