toto je v najnovsom en. manualy priamo z php.net:
HTTP Cookies: $_COOKIE
comment: Introduced in 4.1.0. In earlier versions, use $HTTP_COOKIE_VARS.

An associative array of variables passed to the current script via HTTP cookies. Automatically global in any scope.

This is a 'superglobal', or automatic global, variable. This simply means that it is available in all scopes throughout a script. You don't need to do a global $_COOKIE; to access it within functions or methods, as you do with $HTTP_COOKIE_VARS.