Programming PHP

The global arrays are:
$HTTP_COOKIE_VARS
Contains any cookie values passed as part of the request, where the keys of the
array are the names of the cookies
$HTTP_GET_VARS
Contains any parameters that are part of a GET request, where the keys of the
array are the names of the form parameters
$HTTP_POST_VARS
Contains any parameters that are part of a POST request, where the keys of the
array are the names of the form parameters
$HTTP_POST_FILES
Contains information about any uploaded files
$HTTP_SERVER_VARS
Contains useful information about the web server, as described in the next section
$HTTP_ENV_VARS
Contains the values of any environment variables, where the keys of the array are
the names of the environment variables
Because names like $HTTP_GET_VARS are long and awkward to use, PHP provides
shorter aliases: $_COOKIE, $_GET, $_POST, $_FILES, $_SERVER, and $_ENV. These variables
are not only global, but also visible from within function definitions, unlike their
longer counterparts. These short variables are the recommended way to access EGPCS
values. The $_REQUEST array is also created by PHP if the register_globals option is
on; however, there is no corresponding $HTTP_REQUEST_VARS array. The $_REQUEST
array contains the elements of the $_GET, $_POST, and $_COOKIE arrays.
PHP also creates a variable called $PHP_SELF, which holds the name of the current
script, relative to the document root (e.g., /store/cart.php). This value is also accessible
as $_SERVER['PHP_SELF']. This variable is useful when creating self-referencing
scripts, as we’ll see later.
Server Information
The $_SERVER array contains a lot of useful information from the web server. Much of
this information comes from the environment variables required in the CGI specification
(http://hoohoo.ncsa.uiuc.edu/cgi/env.html).
Here is a complete list of the entries in $_SERVER that come from CGI:
SERVER_SOFTWARE
A string that identifies the server (e.g., “Apache/1.3.22 (Unix) mod_perl/1.26
PHP/4.1.0”).
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