php man page for superglobals

SUPERGLOBALS(3) 							 1							   SUPERGLOBALS(3)

Superglobals - Superglobals are built-in variables that are always available in all scopes

	Several predefined variables in PHP are "superglobals", which means they are available in all scopes throughout a script. There is no need
       to do global $variable; to access them within functions or methods.

	These superglobal variables are:

	      o$GLOBALS

	      o$_SERVER

	      o$_GET

	      o$_POST

	      o$_FILES

	      o$_COOKIE

	      o$_SESSION

	      o$_REQUEST

	      o$_ENV

       +--------+---------------------------------------+
       |Version |					|
       |	|					|
       |	|	       Description		|
       |	|					|
       +--------+---------------------------------------+
       | 4.1.0	|					|
       |	|					|
       |	|  Superglobals were introduced to PHP. |
       |	|					|
       +--------+---------------------------------------+
       Note

	      Variable availability

	       By default, all of the superglobals are available but there are directives that affect this availability. For further  information,
	      refer to the documentation for variables_order.

       Note

	      Dealing with register_globals

	       If the deprecated register_globals directive is set to on then the variables within will also be made available in the global scope
	      of the script. For example, $_POST['foo'] would also exist as $foo.

	       For related information, see the FAQ titled "How does register_globals affect me?"

       Note

	      Variable variables

	       Superglobals cannot be used as variable variables inside functions or class methods.

       variable scope, The variables_order directive, The filter extension.

PHP Documentation Group 													   SUPERGLOBALS(3)