It is absolutely how it works when there is a internal policy against using PHP.

That's literally fact. That's literally how it works.

Additional resource: See also: https://news.ycombinator.com/item?id=23030330

Sure, PHP is against internal policy.

But if you take the initiative to open source a client library in PHP and it gets the attention of AWS it absolutely could result in an interview.

If you are interviewing and you whiteboard your solution in PHP they won't hold it against you. The language is less important than the concepts. Granted, if the only language you know is PHP that could be a risk in your career. I think that holds true for any developer, though.

Source: Used to work and interview at AWS

Yeah, it's literally not how it works, writing code in a banned language doesn't prevent you from getting interviews or being taken seriously.