WordPress is the most widely used content management system (CMS) and website builder, powering more than 40% of the web. It is written in PHP and supports various themes, plugins, and extensions.
Facebook is the largest social networking service, with over 2.8 billion monthly active users. It was initially developed in PHP, and later introduced its own dialect called Hack. Facebook also created the HipHop Virtual Machine (HHVM), a just-in-time (JIT) compiler for PHP and Hack.
Wikipedia is the largest and most popular online encyclopedia, with over 55 million articles in 300 languages. It is powered by MediaWiki, a free and open-source wiki software that is written in PHP and uses MySQL as its database.
Laravel is a modern and elegant web application framework that provides various features and tools for web development. It is one of the most popular PHP frameworks, with a large and active community of developers and users.
Drupal is another widely used CMS that allows users to create and manage websites, blogs, forums, e-commerce, and more. It is written in PHP and supports various modules, themes, and distributions.