Open Source PHP CMS: Contao
Licensed under the GNU Lesser General Public License (LGPL), Contao (also known as TYPOlight) is a free and open source PHP CMS for people who want a professional internet presence that is easy to maintain. The state-of-the-art structure of the system offers a high security standard and allows you to develop search engine friendly websites that are also accessible for people with disabilities.
Contao can be expanded flexibly and inexpensively. Easy management of user rights, the Live Update Service, the modern CSS framework and many already integrated modules (news, calendar, forms, etc.) made Contao one of the most popular open source content management systems on the market.