Any WEB application has to deal with situation when it has to replace the content of the page with content of the custom error page. It could happened when:
- Part of the site is closed for maintenance or debugging;
- Some entity is not available (flagged, in pending status and so on)
- User has no access to some resource

Zend Framework by default doesn't provide any functionality to handle unique for each site situation. Even so it gracefully handles common errors such as application errors or invalid urls.
Approach and solution described here in my opinion allow to handle easily any unique case.

Requirements:
- Relatively easy trigger event with minimalistic code;
- Ability to define custom page for each event;
- Ability to pass to custom page meaningful messages;
- Custom error pages must have access to the params of initial request 
 
 Approach:
 - Each event has dedicated Exception 
 - To trigger event one must throw an exception
 - Message defined in Exception is available for custom error page
 - Error handler helper catches exceptions and forwards to specific action in Error Controller
 - Functionality defined in Actions allows get extra data before rendering view