session_destroy destroys all of the data associated with the current session. It does not unset any of the global variables associated with the session, or unset the session cookie. To use the session variables again, session_start has to be called.
You do not have to call session_destroy from usual code. Cleanup $_SESSION array rather than destroying session data.
In order to kill the session altogether, the session ID must also be unset. If a cookie is used to propagate the session ID (default behavior), then the session cookie must be deleted. setcookie may be used for that.
When session.use_strict_mode is enabled. You do not have to remove obsolete session ID cookie because session module will not accept session ID cookie when there is no data associated to the session ID and set new session ID cookie. Enabling session.use_strict_mode is recommended for all sites.
Although current session module does not accept empty session ID cookie, but immediate session deletion may result in empty session ID cookie due to client(browser) side race condition. This will result that the client creates many session ID needlessly.
To avoid these, you must set deletion time-stamp to $_SESSION and reject access while later. Or make sure your application does not have concurrent requests. This applies to session_regenerate_id also.
This function has no parameters.
Returns true on success or false on failure.
Only use session_unset for older deprecated code that does not use $_SESSION.