class App_Pre extends Zend_Controller_Plugin_Abstract {

    public function preDispatch( Zend_Controller_Request_Abstract $request)
    {
        echo 'a';
    }
}

<?php

// Define path to application directory
defined('APPLICATION_PATH')
    || define('APPLICATION_PATH', realpath(dirname(__FILE__) . '/../application'));

// Define application environment
defined('APPLICATION_ENV')
    || define('APPLICATION_ENV', (getenv('APPLICATION_ENV') ? getenv('APPLICATION_ENV') : 'production'));

// Ensure library/ is on include_path
set_include_path(implode(PATH_SEPARATOR, array(
    realpath(APPLICATION_PATH . '/../library'),
    get_include_path(),
)));

/** Zend_Application */
require_once 'Zend/Application.php';  

// Create application, bootstrap, and run
$application = new Zend_Application(
    APPLICATION_ENV,
    APPLICATION_PATH . '/configs/application.ini'
);

$application->bootstrap()->run();

$front = Zend_Controller_Front::getInstance();
$front->registerPlugin(new App_Pre());
$front->dispatch();