The systems described here isn't directly involved with any PHP code.
Like all Facebook services, they are communicated with over the Thrift RPC system, and may have PHP (or any other language) clients, and may talk to other services using Thrift (or occasionally other protocols), some of which may use PHP.
Like all Facebook services, they are communicated with over the Thrift RPC system, and may have PHP (or any other language) clients, and may talk to other services using Thrift (or occasionally other protocols), some of which may use PHP.
If you're asking a general question about batching requests in PHP, http://docs.hhvm.com/manual/en/hack.async.php may be informative.