UPI marchant open api solution

I am looking for a freelancer who can develop a UPI merchant open API solution using PHP. The ideal candidate should have experience in PHP programming and API integration.

Requirements:
- Develop a UPI merchant open API solution using PHP
- Ability to integrate the solution with my existing system

Skills and Experience:
- Proficient in PHP programming
- Experience in API integration
- Familiarity with UPI merchant open API

Note: I am open to suggestions regarding the specific API to be used.