1. Key Difference 1: Language Support CodeIgniter is based on PHP, which is a popular server-side scripting language. It provides support for a wide range of platforms and operating systems. On the other hand, PHP-MVC is a framework that utilizes the MVC (Model-View-Controller) pattern and is specifically designed for PHP applications.

2. Key Difference 2: Modularity CodeIgniter follows a monolithic approach, where all the libraries and components are bundled together, making it relatively easy to set up and use. However, this can lead to a larger footprint and slower performance for larger applications. PHP-MVC, on the other hand, follows a modular approach, allowing developers to pick and choose the specific components they need, resulting in leaner and more efficient applications.

3. Key Difference 3: Configuration and Convention CodeIgniter relies heavily on configuration files, where developers can define various settings and options. It follows a "convention over configuration" approach, meaning it assumes certain default conventions unless explicitly overridden. PHP-MVC, on the other hand, is more configuration-driven, allowing developers to customize and fine-tune various aspects of the framework to suit their specific needs.

4. Key Difference 4: Database Management CodeIgniter provides a built-in database abstraction layer, which makes it easier to work with databases. It supports multiple database types, such as MySQL, Oracle, and PostgreSQL, and provides a simple and intuitive interface for performing database operations. PHP-MVC, on the other hand, does not have a built-in database layer and relies on third-party libraries or extensions for database management.

5. Key Difference 5: Extension and Customization CodeIgniter provides a robust set of built-in libraries and helpers that cover a wide range of functionality, such as form validation, file uploading, and session management. Additionally, it has a large community of developers who contribute plugins and extensions, making it easy to extend the framework's capabilities. PHP-MVC, on the other hand, provides a basic set of libraries and leaves room for developers to customize and extend the framework according to their specific requirements.

6. Key Difference 6: Learning Curve CodeIgniter has a relatively low learning curve, making it accessible to beginners and allowing them to quickly start building web applications. It has comprehensive documentation and a large community of developers, which makes it easier to find support and resources. PHP-MVC, on the other hand, may have a steeper learning curve, as it requires a solid understanding of the MVC pattern and PHP frameworks in general. However, once mastered, it provides a solid foundation for developing scalable and maintainable applications.

In summary, CodeIgniter is a PHP-based framework that offers simplicity, comprehensive documentation, and a low learning curve, while PHP-MVC provides modularity, customization options, and extensibility for more experienced developers.