Alternative for deprecated session_is_registered

Question

session_start();
if (!session_is_registered(user)) {
    header("Location: login.php");
    die();
}

What is the proper way to do this since session_is_registered() is deprecated?

Answer 1

if (empty($_SESSION['user'])){
    // session user does not exist
}

Answer 2

use if ( isset( $_SESSION['user'] ) ){}

Answer 3

isset() will not do what you want all of the time. It will fail if 'user' is falsy (0, false, null, empty string). array_key_exists() will match the truth table of session_is_registered, despite what php.net says:

if ( !array_key_exists( 'user', $_SESSION ) ){
  /* 'user' is in the session */
}

//in other words...
if ( array_key_exists( 'user', $_SESSION ) === session_is_registered( 'user' ) ) {
  /* This is always executed */
}