Purchase verify System api

Hello
I want to know about the envato api to verify purchase
I am not able to understand the purchase verification api
Can u have any code in php to verify the purchase before installation.
I had also come to know about the old and new api. But i am totally confused please help me

You’ll need to use the Buyer/Purchases API: https://build.envato.com/api/#!/market_0/Buyer_Purchases

Strongly recommend against verification before installation. It’s very complicated, makes the buyer experience bad and slow, and it will stop working if there is an issue with internet connectivity/Envato API/your website. Just spend the time working on your products to make them better.

Thanks for your suggestion actually i am begginer and this was my first script. I had come to know that purchase verify system is very important. Thats why i was doing this. Can u please tell me do i use purchase verify system or not ???