(PHP 5 >= 5.4.0)
SessionHandlerInterface::destroy — Destroy a session
$session_id
   )
   Destroys a session. Called by session_regenerate_id() (with $destroy = TRUE),
   session_destroy() and when session_decode() fails.
  
session_idThe session ID being destroyed.
   The return value (usually TRUE on success, FALSE on failure). Note this value is returned internally to PHP for processing.