Facebook PHP with Keith Adams

Facebook was built using PHP, a programming language that was used widely in the late 90s and early 2000s. PHP allows developers to get web applications built quickly and easily, although PHP has a reputation for being difficult to scale. 

In the early days of Facebook, the company was scaling rapidly on every dimension. 

New users were piling into Facebook. Existing users were increasing their interactions and developing new patterns of usage. The Facebook application was rolling out new features quickly, adding them into the Facebook PHP codebase.

A common pattern for scaling a large software application is to use a microservices architecture, breaking up the monolithic application into small services which can scale independently. For many applications, this pattern works well. But for some applications, microservices makes less sense.

Microsoft Excel is one example. In Excel, a user is making updates to a complex data model using formulas, functions, and other in-app tools that need to be fast, performant, and integrated. The user needs to have a sense that the Excel data model will update quickly in response to changes. 

A software team working on a spreadsheet product such as Excel might prefer to keep all the application logic in a monolithic application. 

A monolith can centralize logic and make it easier to reason about. A monolith can reduce the number of network hops, cutting down on distributed systems problems. Testing and deploying a monolithic application can be less complex than doing so in a distributed, microservices system.

Facebook chose to scale its PHP monolith rather than breaking it up into distributed microservices. Scaling PHP allowed Facebook to continue moving fast without going through a painful refactoring that would have slowed down the entire company. 

The first effort to scale PHP involved transpiling the entire PHP application into C++. This C++ version of Facebook ran faster and with a lower memory footprint. But C++ required ahead-of-time compilation: the PHP codebase had to be converted to C++ in one synchronous step.

The Hip Hop Virtual Machine (HHVM) is a just-in-time compiler that serves as an execution engine for PHP as well as Hack, a language that Facebook created as a dialect of PHP.

HHVM allows for dynamic execution of code that is written in PHP or Hack. The code is first transpiled into HHBC, a high-level bytecode format that serves as an intermediate language. This bytecode is dynamically executed by the HHVM. As a bytecode virtual machine, HHVM has similarities to V8, the JVM, or the CLR.

Keith Adams was an engineer at Facebook for six years, where he helped develop infrastructure to scale PHP effectively. Keith is now the chief architect at Slack, which is also a scaled PHP application. Keith returns to Software Engineering Daily to discuss why and how Facebook scaled PHP.

ANNOUNCEMENTS

  • New SEDaily app for iOS and for Android. It includes all 1000 of our old episodes, as well as related links, greatest hits, and topics. You can comment on episodes and have discussions with other members of the community. I’ll be commenting on each episode, so if you hear an episode that you have some commentary on, jump onto the app, or on SoftwareDaily.com to share your thoughts. And you can become a paid subscriber for ad free episodes at softwareengineeringdaily.com/subscribe. Altalogy is the company who has been developing much of the software for the newest app, and if you are looking for a company to help you with your mobile and web development, I recommend checking them out.    
  • FindCollabs is a place to find collaborators and build projects. FindCollabs is the company I am building, and we are having an online hackathon with $2500 in prizes. If you are working on a project, or you are looking for other programmers to build a project or start a company with, check out FindCollabs. I’ve been interviewing people from some of these projects on the FindCollabs podcast, so if you want to learn more about the community you can hear that podcast.
  • Upcoming conferences I’m attending: Datadog Dash July 16th and 17th in NYC, Open Core Summit September 19th and 20th in San Francisco.
  • We are hiring two interns for software engineering and business development! If you are interested in either position, send an email with your resume to jeff@softwareengineeringdaily.com with “Internship” in the subject line.

Transcript

Transcript provided by We Edit Podcasts. Software Engineering Daily listeners can go to weeditpodcasts.com/sed to get 20% off the first two months of audio editing and transcription services. Thanks to We Edit Podcasts for partnering with SE Daily. Please click here to view this show’s transcript.


Sponsors

G2i is a hiring platform run by engineers that matches you with React, React Native, GraphQL, and mobile engineers who you can trust. Whether you are a new company building your first product or an established company that wants additional engineering help, G2i has the talent you need to accomplish your goals. Go to softwareengineeringdaily.com/g2i

Datadog unites metrics, traces, and logs in one platform so you can get full visibility into your infrastructure and applications. Check out new features like Trace Search & Analytics for rapid insights into high-cardinality data, and Watchdog, an auto-detection engine that alerts you to performance anomalies across your applications. Datadog makes it easy for teams to monitor every layer of their stack in one place, but don’t take our word for it—start a free trial today & Datadog will send you a T-shirt! softwareengineeringdaily.com/datadog

NetSuite is a complete business management software platform that handles sales, financing, accounting, orders, and HR. Netsuite gives you visibility into your business, helping you to control and grow your business. Netsuite is offering a free guide: “seven key strategies to grow your profits” at netsuite.com/sedaily.

GoCD is a continuous delivery tool from ThoughtWorks. If you have heard about continuous delivery, but you don’t know what it looks like in action, try the GoCD test drive at gocd.org/sedaily. GoCD’s test drive will set up example pipelines for you to see how GoCD manages your continuous delivery workflows. Visualize your deployment pipelines and understand which tests are passing and which tests are failing.

Software Weekly

Software Weekly

Subscribe to Software Weekly, a curated weekly newsletter featuring the best and newest from the software engineering community.