Check if PHP session has already started

Question

I have a PHP file that is sometimes called from a page that has started a session and sometimes from a page that doesn\'t have session started. Therefore when I have s

Answer 1

Prior to PHP 5.4 there is no reliable way of knowing other than setting a global flag.

Consider:

var_dump($_SESSION); // null
session_start();
var_dump($_SESSION); // array
session_destroy();
var_dump($_SESSION); // array, but session isn't active.

Or:

session_id(); // returns empty string
session_start();
session_id(); // returns session hash
session_destroy();
session_id(); // returns empty string, ok, but then
session_id('foo'); // tell php the session id to use
session_id(); // returns 'foo', but no session is active.

So, prior to PHP 5.4 you should set a global boolean.