How to check if the site generates requests for other resources?

Question

PHP

Hello.
Task. There is a web site that got from the pre-developers. You need to check if the site makes external requests. Under the exterior, I mean other sites or resources. For example, weather or currency sites, Yandex counters or Google analytics, or some other site.
I've used the devtool chrome Network tab so far joxi.ru/DmB1oL0fMbkVrP But, if I understand correctly, the devtool chrome Network only tracks the frontend part (Jquery Ajax)?
But what if requests go through cURL in PHP scripts?
The site during testing is located on the local web server OpenServer - Apache 2.2 + PHP 5.4. So there is full access not only to the sources, but also to the logs and settings of Apache, PHP.
What tools to use to track any requests for external resources?
How to prove to another developer that he did such a check with 99% accuracy?
UPD#1:
1. Can I use the Chrome Dev Tool for this?
2. Can Apache logs show if requests are going from the site to external? If so, what should I pay attention to in the logs?

Answer 1

Wireshark

Answer 2

Check the browser with any sniffer, run the site and look at the logs. Then the same with OpenServer.