On his blog today Martynas Jusevicius talks about a feature that was new in PHP5 - Exceptions:
A useful new feature in PHP 5 is exception handling via the try/throw/catch paradigm. An exception may be thrown and caught. If an exception is thrown in code surrounded by try, the following statements will not be executed, and the exception will be handled by the first matching catch block.
He gives a high-level overview of how Exceptions in PHP5 work and includes a simple example from his work with his DIY Framework.