Treat division by zero

Question

I have the following function in PHP:

public function teste() {
    $conta = "0/(0+0+0)";
    eval('$result = (' . $conta . ');');
    echo $result;
}

In this case, the formula (in example 0/(0+0+0) obviously returns error because of division by zero. The problem is that this formula is built dynamically and it can happen of division by zero. In this case I would like it to return only zero and not error.

Answer 1

First, you shouldn’t wear eval(). You have to have a very strong domain in programming to use it smoothly. And whoever has this domain always finds a better solution.

Division by zero is considered a programming error, is the same thing as giving a pointer error (PHP does not give it, I think, but it treats in a way that I consider harmful), it should never occur, the solution is to ensure that there is no division by zero, so you must ensure that the divisor is not zero before using it. A simple if before it resolves. But in this case it doesn’t even need to be since you know it’s 0, you don’t have to do it in real code.

Always treating the division by 0 as resulting in 0 is a mathematical error, if this were correct the mathematics would do this. And when it makes sense for some other reason than the mathematician is using the number for a function he shouldn’t have. Again, programming errors should not be treated as if they were normal, or as if they were exceptions.

When catching exception, and in good codes this rarely occurs, never capture Exception, this exception should even be abstract. Maybe everything that serves to inherit should.

See also:

• How to best treat exceptions in Java?
• What are Exceptions?

Answer 2

Putting a Try / catch would not be the solution?

public function teste() {
    $conta = "0/(0+0+0)";
    try {
      eval('$result = (' . $conta . ');');
      echo $result;
    }
    catch(Exception $e) {
      echo 0;
    }    
}