CTools Module

This tutorial shows you how to insert a form into a modal so it pops up on your site after a user clicks a link, without having to write any JavaScript at all. The functionality that supplies this is the CTools module and core ajax functionality in Drupal 7.

Drupal gives ability to access callback. The access callback is executed before the call 'page callback'. Here create custom permission using access callback. The access callback helpfull for specific permissions to users or roles.