Question

Consider the following, simple class constructor. (note that I am obviously not including all methods that are referenced.

// Initialize User class.
public function __construct($user_id = NULL)
{
    // If user is loaded (and a user ID is provided)
    if ($user_id)
    {
        // If user is authorized.
        if ($this->authorized($user_id))
        {
            // Load user information.
            $this->info = $this->load($user_id);
        }
        else
        {
            // Return an empty (nonexistent) user.
            return NULL;
        }
    }

    // If user is loaded (and no user ID is provided)
    else
    {
        // Create a new user.
        $new_user = create_user();

        // Return the new user's ID.
        return $new_user;
    }
}

My question is this: is my method of returning values here wrong? My friend insists that a constructor should ALWAYS return an object NO MATTER WHAT. However, the way I have it laid out here seems much simpler, and is much easier to work with. (If I am making a new user, then I get his ID right off the bat. If I am loading an existing user, I immediately have access to her/his information)

If it IS wrong, why? Why is this bad?

Answer 1

What you’re trying to do simply doesn’t work, the constructor will return the new instance of User anyway, even when you try to return null.

For example, this:

class User {
  function __construct() {
    return null;
  }
}
var_dump(new User());

will print:

object(User)#1 (0) {
}

http://codepad.org/0IdJydkY