[fw-mvc] why setting the $bootstrap variable to TRUE in index.php?

Hi,

The new quick start for ZF 1.6 explains how to create a public index.php
file that will be the only entry point of the application.
This file starts with:

|<?php
// Step 1: Set a flag indicating setup is necessary
$bootstrap = true;
...

Then, the boostrap.php is described and an example is given that starts
with:

||<?php
// Step 1: Check to see if the applicaiton environment is already setup
if (isset($bootstrap) && $bootstrap) {
|...

My question is:
why setting a $bootstrap variable and testing it in the bootstrap file?
As the index.php will be run at every request, the $bootstrap variable
will always be true and the "if" section will always be executed.

Did I miss something?
--

Guillaume ORIOL
goriol@technema.fr