Is FP better than OOP?
FP is stateless means it does not modify the state of the program by return new state every time in immutable fashion while OOP is statefull, its method changes the state of its properties. FP is about having pure function that has no side effects while OOP has side effect as it modify its state.
Is PHP an OOP?
Yes, the latest versions of PHP are object oriented. That is, you can write classes yourself, use inheritance, and where appropriate, the built in functionality is built in objects too (like MySQL features).