Generating random flat colors with php

I want to use flat colors for every categories and It must be random and unique.

I've found that website. => http://ift.tt/2ctcP3k

This is exactly what i need !

How can i generate that with Php? and it would be awesome if It's generate like "Base Flat Color (example. Flat Green)" and with similar other different 25 colors etc. (example. Flat Green Another Tones)