PHP provides the superglobal arrays. They allow you to specify where the input data came from.

• $GLOBALS: Contains a reference to every variable currently available within the global scope of the script. The keys of this array are the names of the global variables.
• $_COOKIE: Values provided to the script with cookies.
• $_GET: A global associative array of variables passed to the script via the HTTP GET method.
• $_POST: A global associative array of variables passed to the script via the HTTP POST method.
• $_FILES: Variables provided to the script via HTTP POST file uploads
• $_SERVER: Variables set by the Web server.
• $_ENV: Variables provided to the script via the environment.
• $_REQUEST: Variables provided to the script via the GET, POST, and COOKIE input types (not considered safe).
• $_SESSION: Variables currently registered to a script's session.

To check the value of a GET submitted field, use $_GET[field]. Likewise, $_POST[field] is used to access a field when using the POST method.