Superglobals — Superglobals are built-in variables that are always available in all scopes
Description
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.
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.
