URL使用PHP路由器重写

Question

I don't using Zend framework, but I found in bootstrap.php file there is the code:

$configRouter = new Zend_Config_Ini(ROOT_SITE.'/configs/'.SITE_NAME.'/configUrl.ini', 'UrlRewrite');
$routers->addConfig($configRouter,'routes');

ConfigUrl.ini file content:

[UrlRewrite]
routes.index.type = "Zend_Controller_Router_Route_Regex"
routes.index.route = ""
routes.index.defaults.module = "www"
routes.index.defaults.controller = "index"
routes.index.defaults.action = "index"

routes.index_captcha.type = "Zend_Controller_Router_Route_Regex"
routes.index_captcha.route = "captcha.jpg[/]?"
routes.index_captcha.defaults.module = "www"
routes.index_captcha.defaults.controller = "index"
routes.index_captcha.defaults.action = "captcha"

routes.index_download.type = "Zend_Controller_Router_Route_Regex"
routes.index_download.route = "download[/]?"
routes.index_download.defaults.module = "www"
routes.index_download.defaults.controller = "index"
routes.index_download.defaults.action = "download"

And the file .htaccess only per line:

Options +FollowSymLinks

But I don't know how it rewrite urls?

Please help me in this way URL Rewriting using PHP!