I agree. I was commenting on Facebook "the social network" and not Facebook the "technology".. :) Anything that can be made to support such large transactions (be it with duct tape and glue) has to have a core capability to support such usage.
Some other languages might allow you to do certain operations in the front-end more easily, but the way to approach it when using PHP might be to delegate that to a back-end service in another language. Similarly, some languages might allow you to write both most front-end and most back-end software in the same language, where PHP might be wholly unsuitable or makes certain things harder to achieve than it is worth using it for (maybe strict memory usage control, maybe where you're looking for CPU cache wins).