PHP creates six global arrays that contain the EGPCS(environment, GET, POST, cookies, and server) information
$_COOKIE
Contains any cookie values passed as part of the request, where the keys of the array are the names of the cookies
$_GET
Contains any parameters that are part of a GET request, where the keys of the array are the names of the form parameters
$_POST
Contains any parameters that are part of a POST request, where the keys of the array are the names of the form parameters
$_FILES
Contains information about any uploaded files
$_SERVER
Contains useful information about the web server, as described in the next section
$_ENV
Contains the values of any environment variables, where the keys of the array are the names of the environment variables
These variables are not only global, but are also visible from within function definitions. The $_REQUEST array is also created by PHP automatically. The $_REQUEST array contains the elements of the $_GET, $_POST, and $_COOKIE arrays all in one array variable