Maintaining two completely separate trading systems — one web-based (written in PHP) and another as part of the game server (written in C++) — would be very complicated. Each would have its own specific problems and both would need to stay in sync whenever changes are made. Here are the main points:

⚙️ Technical Difficulties

1. **Data Synchronization**
- Every time an item is traded or updated, both systems would need to update at the same time.
- This creates risk of inconsistencies (e.g., an item disappearing on one side but not the other).

2. **Maintaining Two Codebases**
- Different bugs in each system.
- Fixes and updates would need to be implemented twice.

3. **Performance & Scalability**
- The C++ system must handle real-time gameplay, while PHP works with asynchronous requests.
- Keeping both in parallel would require a bridge/API to constantly communicate, increasing latency and risk of failures.

4. **Security**
- Two systems = two attack surfaces.
- Exploits could appear if one side is more vulnerable than the other.

🔹 Possible Solutions

1. **Centralize Logic in One System**
- Create a unified API (REST or gRPC) used by both the game and the website.
- The backend handles all trading logic; clients just display and consume data.

2. **Synchronization Layer**
- Use a single central database (e.g., PostgreSQL/MySQL + Redis cache), ensuring both game and website only make requests without keeping their own separate logic.

3. **Modernization**
- Migrate the PHP system to something more modern (Node.js, Go, etc.) or wrap it into microservices that communicate with the C++ server.

✅ **Summary:**
Yes, it would be very difficult and expensive to maintain two separate systems. The ideal solution is to unify trading logic into a single backend that both the web and the game client use. This reduces maintenance, bugs, and security issues.

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💰 **Estimated Cost of Such a Change**

Of course, this depends heavily on the team, scope, and available time. A realistic estimate:

1. **API Planning & Design** – 2 to 4 weeks
- Define endpoints, authentication, and data flow.
- Cost: **$5k – $15k**

2. **Backend Implementation (Unified API)** – 1 to 2 months
- Development in Node.js, Go, or C++ (more expensive).
- Integration with central database.
- Cost: **$20k – $50k**

3. **Game Client Adaptation (C++)** – 3 to 6 weeks
- Replace internal trading logic with API calls.
- Tests to prevent exploits.
- Cost: **$10k – $25k**

4. **Website Adaptation (PHP)** – 2 to 4 weeks
- Refactor to consume the unified API instead of maintaining separate logic.
- Cost: **$5k – $15k**

5. **Testing, QA & Security** – 4 to 6 weeks
- Load tests, exploit prevention, data sync validation.
- Cost: **$10k – $30k**

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📊 **Total Estimated Cost:**
- **Minimum (lean): ~$50k**
- **Maximum (full/professional): ~$135k**

💡 **Required team:**
- 1 backend developer
- 1 C++ developer
- 1 web developer
- 1 QA/tester
- Possibly 1 devops engineer for infrastructure