What is the advantage of using try {} catch {} versus if {} else {}

Question

I am switching from plain mysql in php to PDO and I have noticed that the common way to test for errors is using a try / catch combination instead of if / else combinations.

Answer 1

The advantage of try/catch, and exceptions in general, is more for the people developing libraries like PDO. They allow a system developer to handle undefined situations or unexpected results in a quick and easy way. Take a database connection. What should a system do if the database can't be reached. Should it halt execution? Try again? Throw a warning and continue? The system developer can't know what you'll need it to do, they they throw an exception, which you'll later catch and handle.

The advantage for you, as a consumer of the system is rather than getting some vague error code back, or a simple boolean false that it failed, you get an Exception object which will

1. Be named in such a way that it's more obvious what went wrong (If I remember right, PDO only has one Exception type, but other systems contain multiple exception types for different kinds of errors)

2. May/should contain methods and properties which can help you figure out why the exception was thrown

That's the theory anyway. There are lots of smart people who claim Exceptions are the way to go. There are also lots of smart people who think Exceptions are the devil, and a crutch for lazy system developers. There is nothing resembling consensus on this issue.

Answer 2

Let's say we are writing an a/b division code and the most famous exception case has occurred i.e. 0 divide error, what do you think can be done next? 1. You can print a message and exit. 2. You can print a message and let the user re-enter the values, etc.

There are cases when different people/vendors want to handle the same exception case in different way. The catch block let them do this with ease. If you need to change the way how a certain exception case will be handled, you just need to change the catch block.