protected function generateAuthorizationCode()
    {
        $tokenLen = 40;
        if (function_exists('random_bytes')) {
            $randomData = random_bytes(100);
        } elseif (function_exists('openssl_random_pseudo_bytes')) {
            $randomData = openssl_random_pseudo_bytes(100);
        } elseif (function_exists('mcrypt_create_iv')) {
            $randomData = mcrypt_create_iv(100, MCRYPT_DEV_URANDOM);
        } elseif (@file_exists('/dev/urandom')) { // Get 100 bytes of random data
            $randomData = file_get_contents('/dev/urandom', false, null, 0, 100) . uniqid(mt_rand(), true);
        } else {
            $randomData = mt_rand() . mt_rand() . mt_rand() . mt_rand() . microtime(true) . uniqid(mt_rand(), true);
        }

        return substr(hash('sha512', $randomData), 0, $tokenLen);
    }