array_key_exists（“id”，$ _SESSION）和$ _SESSION ['id]之间的区别;

in this code

if ((array_key_exists("id", $_SESSION) AND $_SESSION['id']) OR (array_key_exists("id", $_COOKIE) AND $_COOKIE['id'])) {

    header("Location: loggedPage.php");

}

I dont know different between them. Can someone explain it to me?

Thanks

Minh Phuc

array_key_exists(“id”, $_SESSION ) :

This lines checks whether id key exists in $_SESSION (Array) and returns true or false.

$_SESSION['id']) :

This lines returns the value of id in SESSION or returns NULL

array_key_exists() checks whether or not a key exists in an array, not caring what value the key might carry. It might carry false, null, 0 and so on..

if($_SESSION['ID']) returns the contents of the variable, after which it is cast as a boolean.

It is proven that isset() is faster than array_key_exists(). The only difference between the two is $key => null will return false on isset() and true on array_key_exists()