Lesson 20 - Custom exceptions in PHP, propagation and the finally block

In the previous tutorial, Exceptions in PHP pt. 2, we learned how to use the built-in PHP exceptions and react to various exceptions in various ways using multiple catch blocks, among other things. Today we are going to finish up learning about exceptions.

Custom exceptions

Since the types of built-in exceptions in PHP are very limited, we will commonly have to create our own exceptions (especially in bigger applications). Creating custom exceptions is pretty simple. All you have to do is inherit a new class from the system's Exception class. Let's make an exception tailor-made for user errors (we'll call it UserException):

class UserException extends Exception
{

}

Its main purpose is to distinguish the exception type, so it doesn't really need any sort of content. We could override our class' __toString() method or we could add our own constructor, but there really is no need to do so.

The main advantage to using custom exceptions is that if and when we catch them, we'd be able to

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