Is $_SESSION['session_id'] always equal to $_COOKIE['PHPSESSID']?

Question

Ultimately, I am trying to understand how best to verify that I am working in the same session as my previous request.

After

start_session()

Which of the following values will have changed if my session (a) has not expired or (b) has expired.

session_id()
$_SESSION['session_id']
$_COOKIE['PHPSESSID']

Answer 1

You can use session_status() :

<?php
    if (session_status() !== PHP_SESSION_ACTIVE) {
      session_start();
    }
?>