About Symfony Request Stack I've read below page multiple time . and also I haven't found another blog post or some thing on web world introduce this Symfony class. "http://symfony.com/blog/new-in-symfony-2-4-the-request-stack"
at the page I mentioned you see a word "sub-request", what do they mean by this word? what do the mean by "more than one request in a single PHP process"?? does it mean a single PHP process which has Symfony Objects in it will handle future request ??
just to close the question I answer my own question thanks to qooplmao and Federkun.
If you use {{ render(controller('SomeBundle:Default:SomeAction')) }} it makes a "sub-request" to the controller meaning the "current request" would not be the "master request". In the request stack both of those request would be available
and here you can read more about subject.