Is PHP still a relevant language in today’s day and age? I know a LOT of languages and it just never occurred to me to learn this one, because anyone I’ve ever been aware of writing a backend these days would either choose Node or one of several compiled languages. Lemmy uses Rust for it’s backend which is highly desireable, many people would have used Golang in the backend world if they desired performance and compilation, otherwise I don’t know why you wouldn’t just use Typescript. Makes it hard to contribute to IMO.
Developer familiarity is a huge pro, of course. But language trendiness is important, too. You can try to code in an obscure language that nobody knows, but you won’t get many useful libraries and frameworks and tools there. You can code in a language that once was popular and has most of the libraries you’ll need, but it will be hard to find other developers to hire or, like here, voluntarily engage in your project.
PHP is still popular enough that these won’t really be problems here, but there sure are cases where developer familiarity won’t beat language trendiness because it will result in much more work or much less helpers.