Do you need an algorithm for calculating the store rating?

Question

PHP

Hello. I can't find the following algorithm.
There is data:
Number of purchases
Total amount of purchases
Number of buyers
Number of unique buyers
Based on these data, it is necessary to display a rating in the range from 1 to 10. Moreover, the algorithm must be balanced.
There are algorithms for calculating user ratings like http://habrahabr.ru/company/darudar/blog/143188/. Something like this is needed.
It is desirable with an example in PHP, if not, it's not scary)
I would be very grateful for the help.

Answer 1

Should this be supported by something?) Well, that is, there should be some explanation why it is done this way, and not that way?)

Answer 2

normalize each parameter and take the arithmetic mean of these four parameters with weights