unsetAll(), nullifyEmptyStrings

unsetAll is a convenience method that will remove all elements specified by the `$keys` array.

nullifyWhiteSpace will convert all strings containing only whitespace to null. Usefull for db inserts when you want to insert null and not an empty string.
Why do you do this?  I don't think you should have a problem with just doing:
```php
foreach ($array as &$value) {
    if (trim($value) === '') {
        $value = null;
    }
}
```