用isset（$ _ SESSION）替换不是session_is_registered（）？

Question

I was working in a login system session_is_registered but this function doesnt work in php5.4+ so I replaced:

   if (session_is_registered('id_user') == true && session_is_registered ('username') == true){}

to

if (isset($_SESSION['id_user']) && isset($_SESSION['username'])){}

...and it works.

But what happens if a want to replace (becouse I need to use this expression)

if (!session_is_registered('id_user') || !session_is_registered('username')){}

Do I need to use !isset() or empty()?

Answer 1

You can use like this way

if (isset($_SESSION['id_user']) && isset($_SESSION['username'])){
      /* this will true if both are set */
}

if (!isset($_SESSION['id_user']) || !isset($_SESSION['username'])){
      /* this will true if one of them is not set */
}

isset will give true if variable is set
empty will give true if variable is set and its blank or null

isset() is NOT equivalent to empty().