harden php sessions - comparison error

Question

I'm trying to harden up my sessions and found the code below. My question is this line isset($_SESSION['last_ip']) !== $_SERVER['REMOTE_ADDR'].

When I echo out the comparison the IP numbers are the same yet that line of code compares the two to be different. If i compare it as != then the comparison works. Why is that? Shouldn't both values be totally identical? Any suggestions how can I fix it so they are ===?

ini_set('session.cookie_httponly', true);
session_start();
if ( isset($_SESSION['last_ip']) === false ) {
    $_SESSION['last_ip'] = $_SERVER['REMOTE_ADDR'];
}
if ( isset($_SESSION['last_ip']) !== $_SERVER['REMOTE_ADDR'] ) {
    echo $_SESSION['last_ip'] . ' / ' . $_SERVER['REMOTE_ADDR']; // the output is identical
}

Answer 1

if ( isset($_SESSION['last_ip']) !== $_SERVER['REMOTE_ADDR'] ) {

You're checking to see if one is set and the other matches that boolean value. Remove the isset.

Answer 2

Personally, i'll be solving this with AND operator in the IF sequence such as:

if ( isset($_SESSION['last_ip']) && $_SESSIOn['last_ip'] != $_SERVER['REMOTE_ADDR'] ) {

Does this helps?