I love PHP, but a red flag?! If they’re busy in the Ruby/Java/C#/Go worlds (all get-it-done environments) then I’d just assume they don’t read many Hacker News praises for PHP. It’s easy to have not encountered it since the bad old days unless you work on a team that uses Laravel for some things.

I do understand hiring someone who has that tradesman programming ethic and is comfortable with Linux, but that’s more requiring certain positive traits.