Warning When Using Superglobal Variables

Hackers often use these to try and inject code etc.  When accessing superglobal variables ensure you sanitise them.  E.g.

  $CameFromPage = htmlentities($_SERVER['HTTP_REFERER']);    //htmlentities() converts things like < > " \ etc into HTML strings like &lt; so they become harmless.

Superglobal Variables

Always available in all scopes

$GLOBALS

References all variables available in global scope

$_SERVER

Server and execution environment information

$_GET

HTTP GET variables

$_POST

HTTP POST variables

$_FILES

HTTP File Upload variables

$_REQUEST

HTTP Request variables

$_SESSION

Session variables

$_ENV

Environment variables

$_COOKIE

HTTP Cookies

$php_errormsg

The previous error message

$HTTP_RAW_POST_DATA

Raw POST data

$http_response_header

HTTP response headers

$argc

The number of arguments passed to script

$argv

Array of arguments passed to script

Full descriptions