Description:
------------
function session_start causes php to send the following line:
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0

This is quite stupid because no browser does care about "post-check=0, pre-check=0". IE will ignore it, as you can read here:
http://blogs.msdn.com/ieinternals/archive/2009/07/20/Using-post_2D00_check-and-pre_2D00_check-cache-directives.aspx
It says: "http://blogs.msdn.com/ieinternals/archive/2009/07/20/Using-post_2D00_check-and-pre_2D00_check-cache-directives.aspx"

And apparently there even was a beta version of IE7 which did download all objects twice when "post-check=0, pre-check=0" was specified.

So, I wonder why it is there in nearly each php page?

Reproduce code:
---------------
<?php
	// Start a session
	if(!defined('SESSION_STARTED')) {
		session_name('a_session_id');
		@session_start();
		define('SESSION_STARTED', true);
	}
?>

Expected result:
----------------
No stupid cache control output

Actual result:
--------------
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0