hello world

If you need this while the user is tying, you're looking for a JavaScript solution. If you need this on the backend, working with unicode is a bit more complicated for PHP since a lot of the built-in functions aren't designed for working with unicode, so you'd need to reach for the mb_* functions and need the mbstring extension enabled. There's probably ways to do this without on the PHP side. But I'd suggest doing this just in JavaScript. The amount of hoops you'd need to jump through to get this working on the PHP side isn't worth it. But I've attached both a frontend and backend solution so you can choose which you need. You can also combine these solutions such as if the user has JavaScript disabled, or an old browser etc.