Federico Cargnelutti

In the same way that set_error_handler( ) sets a handler for uncaught errors, set_exception_handler( ) sets a handler for uncaught exceptions. As exceptions are more powerful than errors, your exception-handling function need only take one parameter: an exception object. From that, you can glean the usual information such as message, line number, etc. Apart from the parameters passed, these work the same as set_error_handler( ). E.g.:

<?php

function handleException($exception)
{
	echo "Caught exception: {$exception->getMessage()}";
}

set_exception_handler("handleException");

throw(new Exception('Testing custom exception handler'));

?>

Having a custom exception handler is a smart move wherever you’re using exceptions, because it essentially captures all exceptions that would otherwise have been uncaught, and gives you one last chance to take some action before the script potentially terminates.

See also: Extending Exceptions

So far, one of the problems with the exception system is all of the exceptions are instances of the same class that only differ by the message they display. This gives us little chance to distinguish between different errors, especially if we localize the error messages into different languages.
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