CodeIgniter App Paystack Integration

I'm looking to integrate Paystack's sandbox mode into my small CodeIgniter app. The job will also include some necessary functionality updates to enhance the app's payment processing capabilities.

Key Requirements:
- Integrate Paystack's sandbox mode
- Add new payment methods to the existing payment processing functionality
- Implement a few functionality updates within the app

Ideal Skills:
- Proficient in CodeIgniter
- Experienced with Paystack integration
- Strong understanding of payment processing systems