PHP provides a large number of predefined variables to any script which it runs. Many of these variables, however, cannot be fully documented as they are dependent upon which server is running, the version and setup of the server, and other factors. Some of these variables will not be available when PHP is run on the command line. For a listing of these variables, please see the section on Reserved Predefined Variables.
In PHP 4.2.0 and later, the default value for the PHP directive register_globals is
off. This is a major change in PHP. Having
register_globals off affects the set of predefined
variables available in the global scope. For example, to get
DOCUMENT_ROOT you'll use
$_SERVER['DOCUMENT_ROOT'] instead of
$_ENV['HOME'] instead of
For related information on this change, read the configuration entry for register_globals, the security chapter on Using Register Globals , as well as the PHP » 4.1.0 and » 4.2.0 Release Announcements.
Using the available PHP Reserved Predefined Variables, like the superglobal arrays, is preferred.
From version 4.1.0 onward, PHP provides an additional set of predefined arrays
containing variables from the web server (if applicable), the
environment, and user input. These new arrays are rather special
in that they are automatically global--i.e., automatically
available in every scope. For this reason, they are often known as
"superglobals". (There is no mechanism in PHP for
user-defined superglobals.) The superglobals are listed below;
however, for a listing of their contents and further discussion on
PHP predefined variables and their natures, please see the section
Reserved Predefined Variables.
Also, you'll notice how the older predefined variables
$HTTP_*_VARS) still exist.
As of PHP 5.0.0, the long PHP
arrays may be disabled with the
Superglobals cannot be used as variable variables inside functions or class methods.
Even though both the superglobal and HTTP_*_VARS can exist at the same time; they are not identical, so modifying one will not change the other.
If certain variables in variables_order are not set, their appropriate PHP predefined arrays are also left empty.
$GLOBALShas existed since PHP 3.
$HTTP_SERVER_VARSarray (which is still available, but deprecated).
$HTTP_GET_VARSarray (which is still available, but deprecated).
$HTTP_POST_VARSarray (which is still available, but deprecated).
$HTTP_COOKIE_VARSarray (which is still available, but deprecated).
$HTTP_POST_FILESarray (which is still available, but deprecated). See POST method uploads for more information.
$HTTP_ENV_VARSarray (which is still available, but deprecated).
Variables provided to the script via the GET, POST, and COOKIE input mechanisms, and which therefore cannot be trusted. The presence and order of variable inclusion in this array is defined according to the PHP variables_order configuration directive. This array has no direct analogue in versions of PHP prior to 4.1.0. See also import_request_variables().
Since PHP 4.3.0, FILE information from
not exist in
When running on the command line
, this will not include the
argc entries; these are
present in the
$HTTP_SESSION_VARSarray (which is still available, but deprecated). See the Session handling functions section for more information.