A simple Snap that checks if an address has a Farcaster account and displays information about that account in the MetaMask transaction flow.
It is published to npm here: https://npmjs.com/package/farcaster-insights
The code for the PHP backend is here: https://gist.github.com/Montoya/77c95bfc8f737f5f6a5b39bb494e96d2
You can view the code and use it for your own projects.