Protecting my code

Hi,

I am currently developing developing several calculators which help users to calculate their optimal setup in a mobile game. (attacks and such)
however, i would like to protect the source code... the actual calculations done based on the values entered by the users.

specs:

• Several variables are filled with values fromform
  
• *Several variables value's are retreived from database (dependant on user input from form)
  
• *static values, now retreived from database aswell
  
• *Calculations, now done in php
  

The parts marked with a * is what i would like to protect
the only thing the users needs is the output of the calculation.

What is the best/recommendedsolution to protect my code?