Matrimonial Site API Development

I need APIs built in core PHP for a matrimonial website to connect with a Java Android application. The APIs should support:

- User authentication
- Profile management
- Matchmaking algorithms

Also, need to integrate payment gateways.

The project requires:
- Connecting the website and Android app
- Ensuring both work perfectly post-completion

No documentation is available, and the previous app developer is no longer available. Ideal skills and experience include:
- Proficiency in core PHP
- Experience in developing APIs
- Knowledge of Java and Android development
- Familiarity with payment gateway integration