How to work with Add-To-Cart functionality?

#1

My code about filterable audio searching, here how can i add Add-To-Cart functionality?

code :
index.php
https://justpaste.it/1qec4

and my

data fetching file,
data_fetch.php

https://justpaste.it/57xxp

How can i add add-to-cart functionality.

Note : In the cart just voice_id, voice_name, not necessary qty & price.

My current output: