Semantic UI - a toolkit for web UI with semantic layout. Actually looks more semantic and clear (in terms of HTML code) than Bootstrap.
Note
slavcodev made autoloader extension to use Upper Case namespaces in Yii2. And now if you really mind it - you can use Yii\Web\Controller instead of use yii\web\Controller.
в MobiDev (Харьков, Украина)
Code in Ruby and Elixir, but still love PHP. Explore ES6 and Vue.js. Explore databases, use Ubuntu and MacOS, think about IT people and management
Заметки
Hand-picked registry of Node.js frameworks. Makes you a suggestion for mature framework to start with a little easier (according to specific of your needs).
PuPHPet - simple GUI to set up virtual machines Vagrant + Puppet for Web development.
Mobile-Detect - a lightweight PHP class for detecting mobile devices. Works like $detect->isMobile() etc., very handy for choosing a frontend rendering strategy based on this info.
Official Elasticsearch client library for Node.js and the browser.