UserFrosting is a free, open-source jumping-off point for building user-centered web applications with PHP and Javascript. It comes with a sleek, modern interface, basic user account features, and an administrative user management system - all fully functioning out of the box.
UserFrosting also has a not-so-secret ulterior motive: to get you to become a better developer. The PHP community has evolved considerably over the past decade, beginning with PHP5's support for object-oriented programming in 2006, to the first meetings of PHP-FIG to develop a set of standards for PHP code, to the release of Composer as the de facto package manager in 2012. At the same time the web development community as a whole has been changing, with websites becoming more dependent on Javascript and CSS to provide sophisticated client-side features.
This breakneck pace has caused a lot of people to get left behind. For someone who hasn't been doing web development continuously for the past ten years, it can feel like a hopeless task to try and get acquainted with all of the new tools and frameworks that seem to be coming out every day. Relevant comic from Abstruse Goose:
The problem is that when you're a busy developer with a lot of Real-Life (tm) projects to work on, it's very difficult to set aside time to read a book about technology X - especially when you're not even sure that you really need to learn X!
UserFrosting has a better idea. Instead of learning about these technologies as a purely academic exercise, you'll work on one of your projects, and learn what you need as you go!
There are three main categories that UserFrosting attempts to cover: software architecture, tools of the trade, and best practices. Most of the PHP developers we see in chat or on Stack Overflow are behind in at least one these areas: