On PHPMaster.com Patrick Mulvey has written up a new tutorial looking at using the PSR-3 logging structure to make a basic logger for your application.

Logging is one of the most ubiquitous tasks encountered in PHP. We use logs to track error messages, record important events, and debug problems with our code. In any PHP project, the code is likely to be full of calls to a logging library which handles these actions for us. [...] To promote compatibility between logging libraries, the PHP-FIG group recently released PRS-3, a common interface for logger objects. In this article, I’ll discuss how the logger interface defined by PSR-3 allows us to write reusable code that isn’t dependent on any particular logging implementation.

He includes a quick introduction to the PSR-3 format, how to get the files you'll need to use it (via Composer). He includes some sample code showing how to make the basic email class with a logger injected for use. Since the Monolog logging project follows the PSR-3 format, it's an easy drop-in option. He also talks about using PSR-3 to avoid having logger dependencies with the "LoggerInterface". There's also a bit at the end of the tutorial showing you how to use the Adapter design pattern to "proxy" the logging calls to the class via a PSR-3 interface.