在Zend中存储应用程序常量的位置？

I have a few constants that I'll need to define for my application, for example, SITE_KEY which would contain a random key for salt passwords.

I'm not sure where I should define those, though. I thought of placing them in public/index.php but that seems a bit messy. Is there a specific place where they should go, according to Zend or something?

Thanks

EDIT

I'm trying to do it this way: In my application.ini I have this:

siteglobal.sitekey = "test"

and in my bootstrap.php file:

protected function _initGlobals()
{
$config = $this->getOptions();
define('SITE_KEY', $config['siteglobal']['sitekey']);

}

Still, this isn't working, when I try to echo SITE_KEY in my controller like this:

echo SITE_KEY;

It doesn't show anything. Any ideas?

In my application, I'm combining both Haim's and Yeroon's approaches. I'm storing application constants in my application.ini, then parsing them in the Bootstrap and putting them into Zend_Registry.

So, in the application.ini

constants.site_key = my_site_key

In the Bootstrap

protected function _initConstants()
{
    $registry = Zend_Registry::getInstance();
    $registry->constants = new Zend_Config( $this->getApplication()->getOption('constants') );
}

Then I can access these constants from any place in the application (model, controller, etc.)

Zend_Registry::getInstance()->constants->site_key

application/configs/application.ini

myvar = myvalue

after get them like :

$myvar = $application->getOption('myvar');