在CodeIgniter 3.x中使用empty（）和isset（）检查会话变量

Question

With CodeIgniter 3.0.3, the documentation states that session data can be retrieved a few different ways, including $_SESSION['item'] and $this->session->item. It's true. No matter how I set the session variable, I see that I can echo the value both ways.

Now, with that session variable populated, I can check for empty condition like this: if(empty($_SESSION['item'])), and it evaluates as bool(false) just as I would expect. However, if I check the same session variable in this manner: if(empty($this->session->item)) it evaluates as bool(true), which is NOT what I expect (since I can echo its value on the very next line). Why are these two different ways of checking for empty condition being evaluated differently?

Answer 1

This is due to how empty() works. Compare this quote:

The result for empty($registry->notEmpty) is a bit unexpeced as the value is obviously set and non-empty. This is due to the fact that the empty() function uses __isset() magic functin in these cases. Although it's noted in the documentation above, I think it's worth mentioning in more detail as the behaviour is not straightforward. In order to achieve desired (expexted?) results, you need to add __isset() magic function to your class:

(taken from php.net: http://php.net/manual/en/function.empty.php, comment from user Janci)