Facebook was originally created by Mark Zuckerberg while he was a student at Harvard University. Zuckerberg launched Facebook from his dorm room on February 4, 2004. Over the years, Facebook has grown into one of the largest and most popular social media platforms in the world, with over 2.8 billion monthly active users as of 2020.
The Initial Language Choice
When Zuckerberg first created Facebook, he chose to build it using PHP. PHP (short for Hypertext Preprocessor) is a server-side scripting language that can be embedded into HTML. Some key reasons Zuckerberg likely chose PHP for Facebook’s initial development include:
- PHP code can be directly embedded into HTML pages, allowing for dynamic content and interactivity.
- PHP is open source and free to use.
- PHP runs on many web servers and platforms.
- PHP can interface with databases like MySQL to store and retrieve data.
- PHP was very common for web development at the time, making resources and hosting widely available.
So by leveraging PHP, Zuckerberg was able to build Facebook quickly and launch it online in just a couple of weeks. The initial version relied heavily on PHP for core functions like user registration, login, profiles, friending, and posting updates.
Scaling Up and Expanding the Stack
As Facebook started to grow rapidly after launch, new languages and technologies were incorporated to help scale up. PHP alone wasn’t robust enough to power all of Facebook’s needs as millions more users joined.
Some key additions to Facebook’s stack in the early years included:
- C++ – Used to build higher performance, lower level services.
- Java – Used for backend services and increased scalability.
- JavaScript – Used to power more complex frontend user interfaces.
- React – A JavaScript library introduced in 2011 to build modular UIs.
- GraphQL – A query language created internally to fetch data from Facebook’s servers.
- HHVM – A virtual machine developed to execute PHP code faster.
- Hive – A data warehouse system to manage massive datasets.
While PHP remained a key part of Facebook’s codebase, these new technologies helped transform Facebook’s architecture into a robust, scalable platform that could handle an enormous userbase.
The Importance of PHP at Facebook Today
Even with the many additions over the years, PHP is still a foundational part of Facebook’s technology stack today. Most estimates suggest that Facebook’s massive codebase still contains millions of lines of PHP code.
PHP continues to power major components like:
- User account registration and authentication.
- The News Feed.
- Comments and chat.
- Notifications.
- Profile pages.
- Sharing functionality.
And many other core services are still enabled by PHP. In fact, when Facebook engineers add new features, they most often choose to write the backends in PHP because of their familiarity and expertise.
The reasons PHP remains so instrumental to Facebook include:
- Engineering familiarity and experience with PHP.
- Ease of making quick iterations and changes.
- PHP’s simplicity compared to lower-level languages.
- The risks and challenges of rewriting legacy code.
- Performance boosts from optimizations like HHVM.
While PHP may not be the most advanced or exciting language, it continues to be a reliable workhorse behind the scenes at Facebook.
The Role of Other Key Languages
Although PHP still powers much of the core backend logic, many other languages now play critical roles in Facebook’s architecture:
JavaScript
JavaScript enhances the frontend user experiences in Facebook’s web and mobile apps. React is used for constructing reusable UI components in JavaScript.
C++
C++ is leveraged for high performance systems like machine learning, search, databases, large-scale data processing, and the multimedia rendering engine.
Java
Java handles several backend services, build tools, ad serving, analytics, and Android mobile app development.
Python
Python is used heavily by Facebook’s engineering teams for data analysis, machine learning, and prototyping.
Go
The Go programming language powers backend services that require networked, distributed, and scalable systems.
Erlang
Erlang is used to build distributed, fault-tolerant systems with high availability and low latency.
Hack
Hack is Facebook’s own programming language derived from PHP focused on speed, efficiency, and type safety.
Reason/OCaml
Reason and OCaml see usage for their safety, stability, and ability to handle complex codebases.
By leveraging a diverse set of programming languages together, Facebook is able to build a secure, high-performance platform at immense scale.
Conclusion
While Facebook relies on a variety of languages today, PHP remains deeply ingrained in their architecture. Much of the core platform continues to be powered by PHP due to its simplicity, developer familiarity, and ease of making incremental changes. But languages like C++, Java, JavaScript, Python, and Go fulfill other key roles in helping Facebook scale up to billions of users.
Facebook will likely continue optimizing and evolving their technology stack, but the early choice to build on PHP means its legacy will persist for years to come.
Although Facebook is built on a diverse tech stack today, engineers estimate that the codebase still contains over 100 million lines of PHP powering user-facing features. So while newer technologies get more attention, good old PHP remains a stalwart workhorse under the hood.
The versatility of PHP together with specialized languages like React, Python, C++, Erlang, and Go enable Facebook to operate reliably at massive scale. And PHP’s simplicity and familiarity means it’s still engineers’ preferred language for rapid iteration on new ideas and features.
For network effects, scale, and rapid innovation, Facebook has found it hard to beat the combination of PHP + specialized languages built up over nearly 20 years. As long as PHP can continue to scale with optimizations like HHVM, it will likely remain a vital part of Facebook’s DNA.
So while hype comes and goes around emerging languages, the banal PHP that powered Facebook’s first lines of code continues churning away behind the scenes. Love it or hate it, Facebook and PHP seem inextricably intertwined for the foreseeable future.