But as the platform evolved, the makers needed to add more agility, scalability and better performance to it. So, they addedmany new programming languages to it.
Loading image... (Courtesy: Python Anywhere News)
At present, while the front-end is PHP, at the backend they use C, C++, Java, and Python. In addition, Erlang is used for Facebook chats. And I am sure there are many other languages like XHP, Haskell, D and Hack that they use in different features, apps and add-ons.
Loading image... (Courtesy: Hacker noon)
All these programming languages are integrated to Thrift framework that enables a seamless communication between them and a consistent experience for the users.
Hope this answers your question.
Loading image... (Courtesy: Extreme Tech)