I had great results recently with ~22 year old PHP: https://simonwillison.net/2025/Jul/1/mid-2000s/

It even guessed the vintage correctly!

> This appears to be a custom template system from the mid-2000s era, designed to separate presentation logic from PHP code while maintaining database connectivity for dynamic content generation.

That's great. Just yesterday I spoke with a developer who refutes Rector on old codebases, instead having an LLM simply refactor his PHP 5.6 to 8.(3 I think). He doesn't even check in Rector anymore. These are all bespoke business scripts that his team have been nursing for two decades. He even updated the Codeigniter framework it's all running on.