Facebook was programmed in HTML (Hyper-Text Mark-up language), CSS (Cascading Style Sheets) and PHP (Hypertext Pre-processor). Zuckerberg decided to use PHP because it was perfectly reasonable at the time of Facebook’s creation
In 2004 web technologies like JavaScript, Ruby, C# etc. existed but weren’t advanced enough to change Zuckerberg’s mind at the time compared to PHP. PHP is a widely used open source, general-purpose scripting language. It was originally designed for use in Web site development. In fact, PHP started life as Personal Home Page tools, developed by Rasmus Lerdorf to assist users with Web page tasks.
PHP proved so useful and popular, it rapidly grew to become the full-featured language that it is today, acquiring the name PHP Hypertext Pre-processor along the way to represent its expanded abilities. Mark Zuckerberg built the first version of Facebook in less than 2 weeks. It was nowhere as functional as Facebook is today. It didn't have messaging, walls, timelines, chats, news feeds, pages, friends or groups. All you could do in it was view other people's profiles, one picture of them, their birthdays and interests. It was like an online repository of bio-data of different people.
