When you have code that is a lot of function calls in a row, the need to always name the return variable, and pass it onto the next function makes some people unhappy e.g. this:
$config = loadConfig();
$dic = buildDic($config);
$app = getApp($dic);
$router = getRouter($app);
$dispatcher = getDispatcher($router, $request);
$logic = dispatchBusinessLogic($dispatcher, $request, new Response());
$render = renderResponse($logic);
$psr7 = buildPsr7Response($render);
$response = emit($psr7);
With a pipe-operator in the language could be re-written as:
$response = loadConfig()
|> buildDic($$)
|> getApp($$)
|> getRouter($$)
|> getDispatcher($$, $request)
|> dispatchBusinessLogic($$, $request, new Response())
|> renderResponse($$)
|> buildPsr7Response($$)
|> emit($$);
Even just seeing a list of functions being called in a row without any ->'s is going to make people feel odd, which isn't a good start for an RFC.
I don't think the examples used in the RFC were great. In particular, the names of the variables really help a reader understand what the code is doing. An example where the numbers are more obviously super-fluous, would help people see why pipe operators are useful.
It's quite likely that maths based examples might be better, and maybe steal some from R.
Right now, it's hard to see an updated RFC passing, though it might do better than previously.
However after function auto-loading becomes a feature of the languge, and people start using 'just functions' more, a pipe-operator would probably have a higher chance of succeeding.
Previous RFCs: