PHP web chat script required - any recommendations?

Hey, I'm trying to find an off the shelf script (either free or small one-off licence) to create a web chat solution.

Ideally looking for php/mysql and using jquery/ajax, and Bootstrap.

I've googled and found a few but none jump out as amazing. and I know there are some Wordpress plugins for it, but really don't want to go near WP.

Does anyone know of a script they'd recommend me trying?