Understanding the scope of variables in PHP

Understanding the scope of a variable

Scopes are scopes that a variable can use or be visible in a script. PHP has 6 basic scope rules:

Built-in super global variables can be used and visible anywhere in the script.

constants, once declared, can be globally visible, meaning that they can be used inside and outside the function.

Global variables declared in a script are visible throughout the script, but not inside the function.

When a variable used inside a function is declared as a global variable, its name is the same as the global variable name.

A variable created inside a function that is declared static cannot be visible outside the function, but can be persisted during multiple executions of the function

A variable created inside a function is local to the function, and when the function terminates, the variable does not exist.

$_get and $_post arrays, as well as some other special variables, have their own scope rules. These are called super global variables, and they can be used and visible anywhere, including internal and external functions. The complete list of super global variables is as follows:

$GLOBALS, an array of all global variables (like the global keyword, which will allow access to globals within a function) $_server, the server environment variable array $_get, the variable array $_post passed to the script by the GET method, Array of variables passed to the script via the Post method $_cookie,cookie variable array $_files, array of variables related to file uploads $_env, array of environment variables $_request, array of variables for all user input, including $_get, $_post, and $_ The input that the cookie contains (but does not include the PHP4.3.0 version after the $_files) $_session, the session variable array

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