Collections\TypeValidator::validateItem PHP Method

    protected function validateItem($item, $target)
    {
        $type = gettype($item);
        $shouldBeCallable = $target === 'callable';
        $isObject = $type === "object";
        $looseObjectCheck = $target === "object";
        //callable must be callable
        if ($shouldBeCallable && !is_callable($item)) {
            throw new InvalidArgumentException("Item must be callable");
        }
        //target isn't callable, object must be an instance of target
        if (!$shouldBeCallable && $isObject && !is_a($item, $target) && !$looseObjectCheck) {
            throw new InvalidArgumentException("Item is not type or subtype of " . $target);
        }
        //a non callable, non object type should match the target string
        if (!$shouldBeCallable && !$isObject && $type != $target) {
            throw new InvalidArgumentException("Item is not of type: " . $target);
        }
    }