Facebook in PHP may very well have been a key behind their success. At the time, Friendster was the big social network but was being overwhelmed by their "frien

Facebook in PHP may very well have been a key behind their success. At the time, Friendster was the big social network but was being overwhelmed by their "friend graph" code. Facebook came out to Harvard only, then any college email, then open to the world. I remember being impressed with how few outages the site had, which were MUCH more common then (pre-cloud). That is mostly kudos to devops but PHP let them build stable code quickly and resolve issues fast. There was a source code leak at one point - a missing tag at the beginning of the page meant the source code rendered as text. That in itself meant their deploy process was garbage but the challenges at the time were mostly around handling scale and traffic spikes. Anyway, the leaked code wasn't very clean or well-organized and definitely showed some of the growing pains. But the fact is, the site progressed and grew and was mostly stable the entire trajectory, no matter what was happening under the hood or behind closed doors.