public function session_read($sessionId)
    {
        // assign the current session id
        $this->sessionId   = (string)$sessionId;
        $this->sessionData = $this->engine->get($this->sessionKey . $sessionId);
        // if the sessionData is "false" set it to be an array (casting would create an array with a false entry)
        if (!$this->sessionData) {
            $this->sessionData = [];
        }

        // session data is set uncompressed
        return $this->sessionData;
    }