try catch

class InvalidArgumentException extends Exception {}
class DivideByZeroException extends Exception {}
 
class Mathlib{
    const OPT_ADD = 1;
    const OPT_SUB = 2;
    const OPT_MUL = 3;
    const OPT_DIV = 4;
 
    public function calc($a, $b, $operation){
        if(! is_int($a))
            throw new InvalidArgumentException('Invalid parameter given! $a must be integer.');
        if(! is_int($b))
            throw new InvalidArgumentException('Invalid parameter given! $b must be integer.');
 
        switch($operation){
            case Mathlib::OPT_ADD: return $a + $b;
            case Mathlib::OPT_SUB: return $a - $b;
            case Mathlib::OPT_MUL: return $a * $b;
            case Mathlib::OPT_DIV:
                if($b == 0)
                    throw new DivideByZeroException('Divide by zero. $b cannot be zero!');
                return $a / $b;
            default: throw new InvalidArgumentException('$opt is not valid!');
        }
    }
}
 
class Math extends Controller{
    function calc(){
        $this->load->library('Mathlib');
 
        // Variabel.
        $x = 10; $y = 7; $opt = Mathlib::OPT_ADD;
 
        try{
            $result = $this->mathlib->calc($x, $y, $opt);
            echo $result;
        }catch(InvalidArgumentException $e){
            // Do some exception handler for invalid argument exception
            echo $e->getMessage();
        }catch(DivideByZeroException $e){
            // Do some exception handler for divide by zero exception
            echo $e->getMessage();
        }catch(Exception $e){
            // Do some exception handler for general exception
            echo $e->getMessage();
        }
    }
}