public function getBitSize()
    {
        // override the detection of the bitsize
        // by checking for an env var and returning early
        if (isset($_ENV['PHANTOMJS_BITSIZE'])) {
            return strtolower($_ENV['PHANTOMJS_BITSIZE']);
        }

        if (isset($_SERVER['PHANTOMJS_BITSIZE'])) {
            return strtolower($_SERVER['PHANTOMJS_BITSIZE']);
        }

        if (PHP_INT_SIZE === 4) {
            return '32';
        }

        if (PHP_INT_SIZE === 8) {
            return '64';
        }

        return (string)PHP_INT_SIZE; // 16-bit?
    }