How to fetch data from database if am using bootstrap nav for filter the button

Question

I am try to fetch product from database based on their categories. What I did first was that I query product category only from the database, for it to be able to select unique categories and create new containers of those categories, that was achieve using array map function , but the problem is that I can't re-query the same query that I have query it to be based on their categories inside the array map function for me to get each product details it returning nothing. Then I try this in the screenshot below still returning all products even if I give the to be "men".
I used bootstrap nav for filtering the product when making the design. If you want to check the code you can I find it here https://github.com/Emoumo-coder/e-commerce-fashion. Thanks in advance.

Answer 1

And what about query: Select product FROM products Where categorie="man"
And instead man you give php variable, which value can be FROM nav or select tag