CodeIgniter is an Application Development Framework - a toolkit - for people who build web sites using PHP.

Codeception is a full-stack testing framework which incorporates acceptance, functional, and unit testing. It uses a simple PHP DSL to describe test scenarios and includes over 20 modules

The official documentation of the popular Symfony2 PHP framework.

An easy-to-read, quick reference for PHP best practices, accepted coding standards, and links to authoritative tutorials around the Web.

A powerful Object relational mapper (ORM) for PHP that sits on top of a powerful database abstraction layer (DBAL).