New on the Zend Developer Zone today there's a new tutorial showing you how to set up a script that uses the Observer design pattern with the help of two bits of functionality from the SPL - SplObserver and SplSubject.

As PHP applications grow into complex object-oriented systems, developers look to create centralized components to execute repetitive tasks. These include logging, emailing, redirects, and more. The Observer pattern is a commonly used design pattern to hook such components into an application during runtime, thereby making them reusable. Since PHP 5.1, there are two interfaces built into the Standard PHP Library (SPL) that can be implemented to use the Observer pattern in your application. They are SplSubject, and SplObserver.

They create an exception handler that implements the SplSubject interface (and its "attach", "detach" and "notify" methods) to let the observers of the instance know when an exception is thrown. Code examples are included of both the basic example and a "Mailer" and "Logger" class that can watch the exception handler.