Assuming you’re using the method demonstrated in the Zend Framework Manual, the first thing you need is to configure the Zend AutoLoader. Add this to the index.php file in your public directory:
// Configure autoloader
require_once ‘Zend/Loader/Autoloader.php’;
$autoloader = Zend_Loader_Autoloader::getInstance();
// Require Smarty Engine
require_once ‘Smarty/Smarty.class.php’; // Assuming that you have the Smarty engine at “library/Smarty”
$autoloader->pushAutoloader(‘Smarty’, ’smartyAutoload’);
Change the following line [...]

Recently I went through and upgraded a website from Zend Framework 1.7 to the latest 1.9 minor version. Everything worked great for the most part (aside from a minor code change involving Zend Filter for requests), but there was one significant change that was a bit of a hassle to fix (i.e. “File not found” [...]