Question

I have read articles upon articles trying to understand what exceptions are used for in php and I have gone through the answers already given in the forum. One of the answers which made atleast some sense to me is this one: Are exceptions in php really that useful?

Here is a simple function for finding the inverse of a integer with and without using exceptions (source):

With exception:

function inverse($x) {
  if ($x==0) { 
     throw new Exception('Division by zero.');
  } else { 
     return 1/$x;
  }
}    

try {
  inverse();
} 
catch (Exception $e) {
  echo $e->getMessage();
}

Without exception:

function inverse($x) {
  if ($x==0) { 
     echo "I'm zero. Don't let me be the denominator."; 
  } else { 
     return 1/$x;
  }
}    

So here is my question, why and when should I use one over the other?

Answer 1

There are various opinions on “when to use an exception”. My personal opinion is:

• If you are working with your own code, theres basically no need to throw exceptions, as you then need to write your own handler for it – which also can be done without throwing an exception.
• If you are developing APIs that other programmers are using, it can be usefull to throw exceptions, so the developer using your code knows, that he has to take care of handling errors, AND gets an idea of what was the error-reason. (instead of just getting null he might catch NumberToSmallException, NotANumberException, ….)

In other words: When you already know how to handle an exception if it would appear – dont throw it. If the handling should be up to another developer, using your code – throw it.

Exceptions should not be used to control the flow of your application logic. Therefore use if / else statements.

But these are just my ten cents.