I understand I cannot put php in corvid code. I am guessing I may be able to put some php code in this unusual spot. Can someone verify this is true before I waste a bunch if time trying this?
I need to talk to a 3rd party back end and have some rock-solid php code that is already written and tested.

This seems like an odd place (accessed via Settings >> Analytics. But it seems I can put non-native corvid code in a custom spot if I go that route. Anyone know?
As David states above, you need to use HTTP Functions if you wanted to use it within Wix as there is no other way of implementing it into your site.
https://www.wix.com/corvid/reference/wix-http-functions.html
https://support.wix.com/en/article/corvid-exposing-a-site-api-with-http-functions
Corvid by Wix | How to Use HTTP Functions to Expose Your Site’s API - youtube video
Otherwise, you will just have to bite the bullet and wait for Wix to possibly implement it sometime in the future, although that might be a long way off anytime soon.
In the meanwhile, you can vote for it here.
https://support.wix.com/en/article/request-using-php-programming-language
Plus see Yisrael’s reply here to a previous post about it which explains it perfectly.
https://www.wix.com/corvid/forum/community-discussion/wix-with-php
Wix does not support PHP, and there are no plans to support it.
Thanks. I have surrendered and am translating the code to javascript.