Argument Validating

[rpanning]

I'm trying to gauge what everyone does for error checking, argument validation in their projects. Not user input validation, of course that needs to be done. I mean like arguments passed to function/methods. Do you check the type of variable and if it's valid? For example, if it's an array do you foreach the array and make sure each element is of valid type? If there are certain options for the value do you make sure it is one of them? Etc..

The main question is, where is the line between error checking and performance?

Example code:

class Test
{
    public function call_me($var1, $var2)
    {
        if (!is_string($var1)) {
            throw new Exception('Needs to be a string');
        }

    if (!in_array($var1, array('option1', 'option2', 'option3'))) {
        throw new Exception('Not a valid option');
    }

    if (!is_array($var2)) {
        throw new Exception('Needs to be an array');
    }

    foreach ($var2 AS $element) {
        if (!is_int($element)) {
            throw new Exception('Each array element needs to be int');
        }
    }

    // Start process what function/method is really for...

}
}

[NogDog]

I can't say I have any hard-and-fast rules, but in general...

If a parameter must be an array, I'll do an is_array() on it, but generally won't go as far as checking each element.

If a parameter must be an integer or a float, I'll cast it to one with (int) or (float), then do any range checking after that.

If it must be a resource ID, I'll check that with is_resource().

If it must be an object, I'll use type hinting.

Other than that, I generally let PHP's loose typing do its thing.