PHP Circuit Breaker class: Test if a service is ready checking status first

This class can test if a service is ready checking status first.

It can keep track of the status of services like databases or remote Web services to determine if they can be accessed normally or they are down for some reason.

The class uses the APC extension to store cached values of the status the services, so applications avoid trying again while the services are down until they are not brought up again.

The class can be configured to try a given number of times until the service being tested is considered to be down.

A timeout period can be configured after which a failed service should get only one more chance to become available.