Fonzo I've educated myself a tiny bit. A question now. Might something like this work? Just to move me in the right direction?
I don't have a PHP server now, but read here https://stackoverflow.com/questions/36245837/is-there-any-way-to-run-php-on-android (as quoted below), that i might be able to load Palapa Web Server on an old Android (that I use as my 'server' for IFTTT). Might that work for a very very simple use case? I just need to send one URL which triggers my action.
Once I have a PHP server, then i can figure out the curl etc etc to tie it together, is my hope.
QUOTE THAT I READ AT LINK ABOVE:
"Okay, this is a bit of a personal recommendation, but I've had success with the free Palapa Web Server, which is essentially a web / mysql server which runs on Android, which will run your PHP scripts, and it will also work offline.
"To use it, install the app, and copy your PHP / HTML files onto your phone. By default, the app uses /sdcard/pws/www/, so if you put your files there, it should pick them up. Then, launch the app, click "Start server", and go to http://127.0.0.1:8080 with your web browser on your android device, and it should work.
"Note that setting up PHPMyAdmin (if you need that for managing databases) can be a bit tricky, as you will need to download the extra packages for it.
"Let me know if it works for you. (Note: I'm not affiliated with this app, I'm just a mostly satisfied user.)"