Let say I have
Mobile 1 (Huawei) - HotSpot (IP: 192.168.10.254)
PC1 (Lenovo) - IP: 192.168.10.12
Mobile 2 (Xiaomi) - IP: 192.168.10.6
Mobile 1 is sharing the internet data to PC1 and Mobile 2.
PC1 should be able to open the PHP web app with address
http://127.0.0.1 and
http://192.168.10.12
Then you can check in your Mobile 2 using a mobile web browser try to open the PHP web app with address
http://192.168.10.12
If you can open, then there should be no problem using okHttpUtils2 from your B4A app in Mobile 2.