magento working of paypal express checkout

i was wondering how paypal Ecc works in magento开发者_如何转开发. When i see the source of the checkout page in magento cart,i do not see a form to send the request to the paypal. COuld some explain me how it works in magento? Thanks

The button on cart page links to the url "STORE.DOMAIN/paypal/express/start/" which is ultimately handled by startAction() method in app/code/core/Mage/Paypal/Controller/Express/Abstract.php. This simply builds a parametrised URL to paypal's servers and redirects the user there.