example to give privs on packages instead of give privs directly on table to user to be better DB Security

In Oracle, a stored procedure executes under the owners identity, not under the identity of the caller. Therefore I have knowed that many applications use packages to execute insert, update, select, delete statements instead of give user privileges directly on table. I'm creating a web application using php and Oracle, but I want to use this programing method, I would like to have some example to help me to understand, do you have one? This method is suitable on web applications?