"You can configure the built-in webserver to fork multiple workers in order to test code that requires multiple concurrent requests to the built-in webserver."

"You can configure the built-in webserver to fork multiple workers in order to test code that requires multiple concurrent requests to the built-in webserver." The built-in web-server itself was released with PHP 5.4 (2012). The only thing new about it is support for multiple workers to make it faster for concurrent request handling. But, it's still only intended for development environment and testing. I imagine multiple-workers support is very useful with SPA development, and especially improves testing speed if you run concurrent tests that rely on built-in web-server.