app\models\LegacySession::loadFromRequest PHP Method

    public static function loadFromRequest($request)
    {
        $sessionId = $request->cookie('phpbb3_2cjk5_sid');
        $sessionIdSign = $request->cookie('phpbb3_2cjk5_sid_check');
        if ($sessionId === null || $sessionIdSign === null) {
            return;
        }
        if ($sessionIdSign !== static::signId($sessionId)) {
            return;
        }
        return static::where('session_ip', $request->getClientIp())->find($sessionId);
    }

 public function legacySession()
 {
     if ($this->_legacySession === false) {
         $session = LegacySession::loadFromRequest($this->request);
         if ($session !== null && $session->session_user_id !== $this->user->user_id) {
             $session = null;
         }
         $this->_legacySession = $session;
     }
     return $this->_legacySession;
 }