Slimframework: a nice and cool microframework
Symfony: a bigger framework which is filled with great and reusable components
Guzzle: a simple and easy to use HTTP client
PHPUnit: a framework for unitary testing
Behat: a framework for Behavior-Driven Development
PHPCS/CBF: code sniffer and code beautifier
Faker: fake data generator
Psysh: a runtime developer console (CLI) full of amazing features
Composer: dependency management and other useful features
Twig: template engine
