First of all, your checkboxes should not have the same ids.
Your method is not particularly scalable, with the overhead for your related products data growing as you hit each power of 10. What I would recommend is that you instead have multiple rows per product_id. You can then use in_array() to find if the products related key is in the results you now have.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.