feat: implement user guide documentation in multiple languages and add IPC infrastructure for UI components

docs/user-guide/en/php.md

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+# PHP Versions & Extensions Management
+
+Multi-PHP makes it easy to switch, configure, and manage different PHP environments for your projects.
+
+---
+
+## 🔩 Managing PHP Versions
+
+Navigate to `Settings > PHP Versions` to download, select, and manage multiple PHP versions.
+
+- **Available Versions**: List of all PHP versions available for download.
+- **Downloaded Versions**: Versions already present on your system.
+- **Default Version**: The global PHP version typically used for CLI (e.g., in a terminal).
+- **Restart Delay**: Multi-PHP automatically restarts PHP-FPM when settings change.
+
+---
+
+## 🛠️ PHP Extension Manager
+
+Every PHP version in Multi-PHP comes with its own extension manager. You don't need to manually edit `php.ini` for common tasks anymore.
+
+### Using the Manager:
+1.  **Select Extension**: Find your desired extension (e.g., `mysql`, `gd`, `zip`).
+2.  **Toggle**: Click to enable or disable the extension.
+3.  **Apply**: Multi-PHP will update the `php.ini` file for you and restart the version's service automatically.
+
+---
+
+## 📝 Raw Editing of `php.ini`
+
+If you need fine-grained control over your PHP configuration, use the built-in **RAW EDITOR**.
+
+1.  **Open Editor**: Access the editor button in the extensions window.
+2.  **Save & Restart**: Click "Save and Restart" to apply changes immediately.
+3.  **Search & Replace**: Use the search functionality to find specific variables like `memory_limit` or `max_execution_time`.
+
+> [!TIP]
+> You can also use the **"Server Tuning"** tool under the "Tools" menu to quickly adjust common PHP performance settings without manually editing code files.
+
+### 📖 Next Steps
+- [Learn how to manage MariaDB Databases](./database.md)
+- [Configure Web Servers](./web-servers.md)
+- [System Integration](./settings.md)