Q:

What is the difference between "render a view" and send the response using the Response's method "sendResponse()"?

I've asked a question about what is "rendering a view". Got some answers:

Rendering a view means showing up a View eg html part to user or
  browser.

and

So by rendering a view, the MVC framework has handled the data in the
  controller and done the backend work in the model, and then sends that
  data to the View to be output to the user.

and 

render just means to emit. To print. To echo. To write to some source
  (probably stdout).

but don't understand then the difference between rendering a view and using the Response class to send the output to the user using its sendResponse() method. If render a view means to echo the output to the user then why sendResponse() exists and vise versa? sendResponse() exactly sends headers and after headers outputs the body. They solve the same tasks but differently? What is the difference?

A:

In ZF, rendering a view doesn't actually output any content.  Instead the rendering process returns the content as a string to the caller.  Zend_Application automatically takes care of taking the rendered view and inserting it into your layout (assuming you use layouts) through a placeholder, and putting that data into the Zend_Controller_Response_Http object which is ultimately responsible for delivering the content to the user.  The reason for the Response object is so it can encapsulate your HTML output, and also manage any additional HTTP headers or redirects you want to send.
You can also manipulate further the contents of the response in the Response object prior ot sending the data to the client if you wish.
sendResponse() takes care of sending any headers (including the HTTP response code), checking for any exceptions that may have occurred (due to not being able to send headers or other reasons) and then sends the HTML which could include your layout and one or more rendered view scripts.
Hope that helps.

