Awesome PHP Libraries

A list of amazingly awesome PHP libraries that you should be using:

Packagist - A package and dependency manager.
Symfony2 - A framework comprised of individual components.
Symfony2 Components - The components that make Symfony2.
Silex - A micro framework built around Symfony2 components.
Silex Propel ServiceProvider - A Silex Propel ORM service provider.
Silex Extensions - A set of Silex extensions.
Twig - A comprehensive templating language.
SwiftMailer - A mailer solution.
Pimple - A tiny dependency injection container.
Doctrine - A comprehensive DBAL and ORM.
Propel - A fast ORM.
Goutte - A simple web scraper.
Assetic - An asset manager.
Imagine - An image manipulation library.
Monolog - A comprehensive logger.
Behat - A Behaviour Driven Development framework.
Mink - Web acceptance testing.
Buzz - A HTTP client.
Guzzle - Another HTTP client.
PHPUnit - A unit testing framework.
Pirum - A PEAR channel manager.
Sismo - A continuous testing server.
KnpMenu - A menu library.
Gaufrette - A filesystem abstraction layer.
Snappy - A PDF and image generation library.
Pagerfanta - A pagination library.
Phly Mustache - A mustache template implementation.
GeoCoder - A geocoding library.