What is the difference between session variables & Global variables in php? [closed]

Question

What is the difference between session variables and global variables in PHP?

Answer 1

Global variables are variables that can be accessed from anywhere in the application, as they have global scope.

Session variables are can also be accessed from anywhere in the application, but they are different for different users, since they depend on the session. They die when a particular user session ends.

Answer 2

global is just a keyword to access a variable that is declared in the top level scope and isn't available in the actual scope. This hasn't anything to do with the session: do not persist between pages.

$a = "test";
function useGlobalVar(){
    echo $a;   // prints nothing, $a is not availabe in this scope
    global $a;
    echo $a;   // prints "test"
}

$GLOBALS is another way to access top-level scope variables without using the global keyword:

$a = "test";
function useGlobalVar(){
    echo $GLOBAL['a'];   // prints "test"
}

There's a bit of of confusion between global and superglobals: Superglobals (like $GLOBALS, $_REQUEST, $_SERVER) are available in any scope without you having to make a global declaration. Again, they do not persist between pages (with the exception of $_SESSION).

$_SESSION is a Superglobal array that persist across different pages.