Detect if PHP session exists

Facebook now offer subscriptions to users so you can get realtime updates on changes. If my app receives an update, I plan to store it in the database. I would also like to detect if their session exists. If it does then I could update the data in there too.

My session IDs are MD5(fb_id + secret) so I could easily edit their session. The question is how can I detect if the session exists.

Solution 1:

I use a combined version:

if(session_id() == '' || !isset($_SESSION) || session_status() === PHP_SESSION_NONE) {
    // session isn't started
    session_start();
}

Solution 2:

According to the PHP.net manual:

If $_SESSION (or $HTTP_SESSION_VARS for PHP 4.0.6 or less) is used, use isset() to check a variable is registered in $_SESSION.

Solution 3:

If you are on php 5.4+, it is cleaner to use session_status():

if (session_status() == PHP_SESSION_ACTIVE) {
  echo 'Session is active';
}

• PHP_SESSION_DISABLED if sessions are disabled.
• PHP_SESSION_NONE if sessions are enabled, but none exists.
• PHP_SESSION_ACTIVE if sessions are enabled, and one exists.

Solution 4:

Which method is used to check if SESSION exists or not? Answer:

isset($_SESSION['variable_name'])

Example:

isset($_SESSION['id'])