Question

Suppose I’m creating a session class, with relevant implementation as below:

public class Session()
{
    private $id;
    private $user;
}

The $user field contains an object of type User if the session is logged in, and is null if the session is not logged in to the site. The $id is the session id.

Suppose I now want to find out whether or not the user is logged in. Obviously I could check to see if $user is null, if it is then the user isn’t logged in – something like this:

public class Session()
{
    private $id;
    private $user;

    public function isLoggedIn()
    {
        return !is_null($user);
    }
}

Alternatively, I could store a boolean session variable, $loggedIn or something, set to false on log in and otherwise initialised in the constructor to be false to test against instead:

public class Session()
{
    private $id;
    private $user;
    private $loggedIn;

    public function isLoggedIn()
    {
        return $loggedIn;
    }
}

Would one approach produce better performance than the other here? If so, which, and why? Alternatively, is one approach preferable to the other for any reason unrelated to performance?

Answer 1

Simpler is better. If you introduce a new variable to track whether or not $user is null, then you also introduce the possibility that is_null($user) and $loggedIn don’t match. Avoiding the hassle of having to worry about that is worth much more than any possible micro-optimization you may gain in performance.