Running the following code on Windows Vista (I know, I know), PHP 5.3.9, the ReflectionClass constructor actually throws a ReflectionException when the desired class cannot be instantiated:
<?php
try {
$ReflectedClass = new ReflectionClass('NonExist');
} catch (LogicException $Exception) {
die('Not gonna make it in here...');
} catch (ReflectionException $Exception) {
die('Your class does not exist!');
}
?>