The constants below are defined by this extension, and will only be available when the extension has either been compiled into PHP or dynamically loaded at runtime.
SID
    (string)
   "name=ID" or empty string
     if session ID was set in an appropriate session cookie. This is
     the same id as the one returned by session_id().
    
   PHP_SESSION_DISABLED
    (int)
   PHP_SESSION_NONE
    (int)
   PHP_SESSION_ACTIVE
    (int)