Question

I have never used Try-catch in my code before, but now I need to do it and it seems that I don’t quite understand the way it works. I have data in a string which I get using explode:

$groupNumbers = array();
$str = $dataGroups['groups'];
$groupNumbers = explode(",", $str);
$count = count($groupNumbers);

Then I want to check if every element is numeric, and if it is I proceed with a database query, otherwise I want to abort the action ant return some error.

Here is what I’m doing:

for ($i = 0; $i < $count; ++$i)
    {
        try
        {
            is_numeric($groupNumbers[$i]);

        }
        catch (Exception $ex)
        {
            process_exception_to_json($ex);
        }
    }

and if evrery element is numeric I construc an active record to do SQL:

$this->db->insert_batch(‘users_groups’, $datas);

Obviously written like that, even if an element is not numeric the action is not aborted and I the insert_batch is still executed with unvalid values which is waht I want to avoid. What is the exact way of doing this, so I can get an exception, and abort the action at the same time.
Thanks

Leron

Answer 1

This is because is_numeric^Docs does not throws an exception but returns a value. It will never fail / throw an exception.

You would need to do it this way (just an example, I don’t suggest it as it’s superfluous):

try
{
    if (!is_numeric($groupNumbers[$i])) {
        throw new RuntimeException('Not numeric.');
    }

}
catch (Exception $ex)
{
    process_exception_to_json($ex);
}

Instead create your own group numbers type:

try
{
    $groupNumbers = GroupNumbers::createFromString($dataGroups['groups']);
}
catch (Exception $ex)
{
    process_exception_to_json($ex);
}

With the following type:

class GroupNumbers extends ArrayObject
{
    public function construct(Array $numbers) {
        foreach ($numbers as $number)
        {
            if (!is_numeric($number))
            {
                throw new InvalidArgumentException(sprintf('Not numeric "%s".', $number));
            }
        }
        parent::__construct($numbers);
    }
    public static function createFromString($string) {
        return new self(explode(",", $string));
    }
}

The string processing is now encapsulated, no more outer-loops and GroupNumbers does only instantiate if there are actual numbers in the string.

If you’re not fluent with classes, you can have similar benefits as well with a procedural style. It’s probably easier to understand (but pretty much the same):

try
{
    $groupNumbers = GroupNumbers_createFromString($dataGroups['groups']);
}
catch (Exception $ex)
{
    process_exception_to_json($ex);
}

function GroupNumbers_createFromString($string)
{
    $numbers = explode(",", $string);
    foreach ($numbers as $number)
    {
        if (!is_numeric($number))
        {
            throw new InvalidArgumentException(sprintf('Not numeric "%s".', $number));
        }
    }
    return $numbers;
}