Also, for high-traffic websites, that's really not a great idea. You might say "but Facebook, PHP" - I'm really certain that their current codebase doesn't have a thread that blocks on DB for each user request.
What does this mean? .NET has been around before SOA was a term and microservices is an evolution of that. The concepts are orthogonal and you could write microservices in PHP, if you really wanted. Like Java, the .NET runtime and platform is highly efficient. That's what .NET has historically had over PHP/Python/Ruby, but I don't keep up with the PHP and Ruby platforms these days.
I feel like this is another one of those discussions like the "Python GIL problem." Whether it's a really a problem depends on the circumstances, and the circumstances were it is a problem affects fewer people than the HN threads suggest.
I'd be willing to bet more projects have been killed by trying to architecture for performance up front than have been killed by being too successful for their own good and keeling over.
If Twitter could make it past the Fail Whale days, I think most of us can too.