blockchain – How to validate transactions in a website?

I’m learning about Bitcoin.

Now, I have to build a website where some transactions have to be verified. I don’t need to create transactions, mine, or something else, just to verify that the transaction was done.

So basically, I know HTML, PHP, JS, etc. But I still don’t know how to check if a particular transaction was made. I read Jimmy Song’s “Programming Bitcoin”, I find Python very useful there. I read the Bitcoin Core developer site as well, but still don’t get it. I don’t want to build a web application from scratch to do specialized things like mining, creating transactions, managing wallets etc, so I’d like to use a well-known API to perform the simple task of checking if a transaction was done.

I’d like to use that API in a PHP application, and in a future in a c ++ application. There’s something like that? Or any PHP code, c ++ where a query against the blockchain is displayed to validate transactions …..