I got so fed up with phpmyadmin, I wrote my own version of this kind of thing. It's not one file though, and only satisfies my specific use cases (although it can browse/search tables, create, edit and delete databases, tables and keys). PHPMyAdmin is so aggressively awful. Writing my own thing for it, I was most surprised by how slow it is. I figured it was just innate to the queries being run to display the metadata required, but nope, my own tool turned out to be way faster.

I also really hate that it doesn't support opening new tabs properly, and the frame-sidebar table listing that goes out of sync with the actual database if you edit tables. also why is the default number of tables listed so low?? I'm all for more competition in this space