Slot machine Random generator

so i saw this: https://www.quora.com/What-algorithm-do-slot-machines-use

How is acually these random numbers generated, and how are the acually translated further on?

i was planning to make a basic slot machine, but no idea where to start.

Well, i had an idea to use something like:

$randomNumber1 = rand(1,X);

for each slot, but that dont seem very effective, How would i solve this?

By the way, here is one image from the link above, that conserns my issue.