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Unit 9: Web Techniques

$HTTP_ENV_VARS Notes
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.

Self Assessment

Multiple choice questions:

1. A simple request for a document or resource residing at a specific URI is called
(a) SET (b) POST
(c) GET (d) None of these
2. A request that is only looking for HTTP header information on the resource, not the
resource itself is called
(a) SET (b) POST
(c) HEAD (d) None of these
True or False:
3. PHP can provide dynamic content according to browser type.
(a) True (b) False
4. PHP creates a separate global variable for every form parameter, every piece of request
information, and every server configuration value.
(a) True (b) False

9.3 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.
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”).
SERVER_NAME

The hostname, DNS alias, or IP address for self-referencing URLs (e.g., “www.example.
com”).

GATEWAY_INTERFACE
The version of the CGI standard being followed (e.g., “CGI/1.1”).

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